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MEMORANDA 



OF 



PHYSIOLOGY 



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HENRY ASHBY, M.D. (Lond.) 

Physician to the Genera Hospital for Sick Children, Manchester ; 

Lecturer on Animal Physiology to the Evening Classes 

The Owens College ; 

Formerly Demonstrator of Physiology, Liverpool School of Medicine 



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THIRD EDITION, THOROUGHLY REVISED, 

WITH 

ADDITIONS AND CORRECTIONS BY . 






V- ; 



AMERICAN EDITOR Y RIG/- 



NEW YORK ,c 

william woodv4 Company 

1882 



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COPYRIGHT 

WILLIAM WOOD & COMPANY 



Teow's 

Printing and Bookbinding Company 

201-213 East 12th Street 

NEW YORK 



PREFACE 



TO 



THE THIBD EDITION. 



Another edition having been called 
for, the text has been revised, and new 
matter added in several of the sections. 



H. A. 



St. John Street, Manchester, 
March, 1881. 



PREFACE 

TO 

THE SECOND EDITION. 



In preparing the Second Edition, the 
text has been carefully revised, some 
new matter added, and several sections 
entirely re-written. 

H. A. 

Manchester, March y 1880. 

I 



PEEFACE 



TO 



THE FIEST EDITION. 



These Memoranda were originally 
compiled for the use of students of the 
Liverpool School of Medicine, when pre- 
paring for the primary examination of 
the College of Surgeons. They now 
appear in print, in the hope that they 
may prove useful to a wider class of stu- 
dents. The information they contain is 
founded, to a large extent, on Quain's 
" Anatomy" (8th ed.), Gray's " Anat- 



VI PKEFACE. 

omy, and Foster's " Text-Book of 
Physiology," to which works the stu- 
dent is referred for his general read- 
ing. 

H. A. 

Manchester, September, 1878. 



CONTENTS. 



SECTION I. 

PHYSIOLOGICAL CHEMISTRY. , 

PAGE 

Inorganic Salts — Organic Salts — Su- 
gars — Fats — Albuminous Compounds 
— Albuminoids, .... 1-19 

SECTION II. 

PHYSIOLOGICAL HISTOLOGY. 

Epithelium — Pigment — Connective 
Tissue — Retiform Tissue — Cartilage 
— Bone — Muscle — Skin and Append- 
ages, 20-55 

SECTION III. 

THE BLOOD. 

Corpuscles— Liq. Sanguinis — Serum — 
Gases — Coagulation, . . . 56-68 



Vlll CONTENTS. 

SECTION IV. 

THE CIRCULATION. 

PAGE 

A Cardiac Revolution— The Valves — 
Sounds of the Heart — The Arteries 
— The Capillaries — The Veins — In- 
nervation of the Heart and Arteries, 69-93 

SECTION V. 

LYMPHATIC SYSTEM. 

Structure — Origin — Lymphatic Glands 
— Lymph — Chyle — Movements of 
Lymph, 94-101 

SECTION VI. 

RESPIRATION. 

Trachea and Bronchi — Lungs— Mech- 
anism of Respiration — Vital Capacity 
— Changes of Blood and Air in Res- 
piration — Excretion of C0 2 — Apnoea 
— Eupncea — Dyspnoea — Asphyxia — 
Coughing— Sneezing — Hiccup, . 102-119 



CONTENTS. IX 

SECTION VII. 

ANIMAL HEAT. 

PAGE 

Cold-blooded Animals — Warm-blooded 
Animals — Processes by which Heat is 
gained and lost — Comparative Tem- 
perature of the Blood of the Body, . 120-124 

SECTION VIIL 

FOOD. 

Nitrogenous — Fats — Starches — Inor- 
ganic Materials- — Dietetics — Milk — 
Standard Diet — Starvation, . . 125-138 

SECTION IX. 
DIGESTION. 

Teeth — Temporary Set — Permanent 
Set — Development — The Tongue — 
Mastication — Saliva — Deglutition — 
CEsophagus — Stomach— Gastric Juice 
Vomiting — Small Intestine — Bile — 
Pancreas — Pancreatic Juice — Large 
Intestine — Defecation —Summary of 
Digestive Changes, .... 139-173 



X CONTENTS. 

SECTION X. 

ABSORPTION AND NUTRITION. 

PAGE 

Absorption of Albuminous Foods, Fats, 

Starches, . . . . . . 174-178 

SECTION XI. 

THE LIVER. 

Structure — Functions — Glycogen — 
Diabetes— Functions in Foetus, . 179-187 

SECTION XII. 

THE KIDNEYS. 

Structure— -The Urine — Its Constitu- 
ents, . 188-200 

SECTION XIII. 

THE DUCTLESS GLANDS. 

Spleen — Structure and Functions — Su- 
prarenals— Thyroid Gland, • . 201-207 



CONTENTS. XI 

SECTION XIV. 

NEKYOUS SYSTEM. 

PAGE 

Nerves — Terminal End Organs — Struc- 
ture of the Central Organs — Proper- 
ties and Functions of Nerves — Nerve- 
Centres — Reflex Actions — Spinal 
Cord — Medulla Oblongata — Func- 
tions of Medulla — The Corpora Qua- 
drigemina — The Cerebellum — Basal 
Ganglia — The Cerebrum — Cranial 
Nerves — Sympathetic, . . . 208-258 



SECTION XV. 

THE SENSES. 

Smell — Taste — Touch — Sight — The 
Eye — Accommodation — Hearing — 
The Ear, 259-280 



SECTION XVI. 

SPEECH. 

The Larynx — Voice — Articulate — 
Sounds, 281-287 



CONTENTS. 



SECTION XVII. 



ORGANS OF GENERATION. 



PAGE 



Uterus — Ovaries — Ovum — Menstrua- 
tion — Corpus Luteum — Impregna- 
tion — Segmentation of Ovum — Chan- 
ges occurring in the Uterus — The 
Placenta — Fetal Circulation — Chan- 
ges at Birth — Mammary Glands — The 
Testes, ...'... 288-306 



APPENDIX. 

Ingesta and Egesta — Metric System — 

Thermometer Scales, . . . 307-309 

INDEX, . . . . . . 311 



MEMORANDA OF PHYSIOLOGY. 



Section 1. 
PHYSIOLOGICAL CHEMISTEY. 

The ultimate constituents of the human body 
comprise some fifteen or sixteen of the ele- 
ments. They are — 

Oxygen Sulphur Sodium Silicon 

Hydrogen Phosphorus Potassium Fluorine 

Carbon Chlorine Magnesium Lifchium 

Nitrogen Calcium Iron Manganese 

These elements are combined in various pro- 
portions, to form the compounds which exist in 
the tissues of the body. The simpler bodies are 
crystalline, as urea ; the more complex, as al- 
bumen, are amorphous. The former, being 
crystalloids, readily pass out of the body through 



2 MEMORANDA OF PHYSIOLOGY. 

the excretory organs ; the latter, being colloids, 
are better suited to form part of its tissues. 

They may be divided into the following 
classes : — 

I. Inorganic Salts. 
II. Organic Crystalline Salts. 

III. Carbo-hydrates, or Sugars. 

IV. Hydro-carbons, or Fats and their 
allies. 

V. Albuminous, or Proteid Compounds. 
VI. Albuminoid, or Gelatinous Com- 
pounds. 

I. The Inorganic Salts include the bases 
before mentioned in combination with acids, the 
principal being chlorides, carbonates, phos- 
phates, and sulphates ; sulphocyanides, fluo- 
rides, and nitrates occur in small quantities. 

II. The Organic Crystalline Bodies are 
very numerous ; for the most part they are the 
result of the disintegration of albuminous mate- 
rial, and nearly all contain nitrogen. The 
principal members of this group are urea, uric 
acid, xanthin, hypoxanthin, hippuric acid, kre- 
atin, kreatinin, lactic acid, lecithin, neurin, 
cerebrin, leucin, ty rosin, and cholesterin. 

Urea, CH 4 N 2 or (NH 2 ) 2 CO, forms the chief 
constituent of the solid portions of the urine. 



MEMORANDA OF PHYSIOLOGY. 3 

It exists also in small quantities in the blood 
and liver, liq. amnii, and serous fluids. 

Preparation — artificially : By heating a mix- 
ture of potassic ferrocyanide and manganic 
dioxide on an iron sheet, potassic cyanate is 
formed, and is dissolved out with water. The 
potassic cyanate is treated with ammonium 
sulphate, ammonium cyanate and potassic sul- 
phate being formed; the potassic salt is re- 
moved by crystallization, and the mother liquor, 
on evaporation to dryness, and extraction of 
the dried residue with alcohol, yields urea. 

From urine : The urine is evaporated to a 
thin syrup, and its own volume of colorless 
nitric acid added ; nitrate of urea is formed and 
readily crystallizes. The nitrate is decolorized 
by animal charcoal and recrystallized. To ob- 
tain the urea pure, the nitrate is decomposed by 
potassic carbonate, the potassic nitrate which is 
formed is allowed to crystallize out, and the 
liquor containing urea evaporated to dryness 
and extracted with alcohol. 

Properties. — Urea crystallizes from water in 
long thin colorless needles. If formed slowly 
the crystals are four- sided, and have pyramidal 
ends. It is a colorless substance of saline taste, 
soluble in water and alcohol, insoluble in ether. 
Urea is closely related (being isomeric) with 



4 MEMOKANDA OF PHYSIOLOGY. 

ammonium cyanate, NH 4 CNO, and carbamide, 
(NH 2 ) 2 CO. 

Characteristic reactions. — (1 . ) Pure nitric acid 
gives in a strong solution of urea a crystalline 
precipitate of urea nitrate. These crystals are 
colorless six-sided prisms, and are sparingly « 
soluble in alcohol. 

(2.) Mercuric nitrate gives a white precipi- 
tate in the absence of chlorides. 

(3.) Nitrous and hypobromous acids decom- 
pose urea, nitrogen and carbonic acid being 
liberated. 

(4.) Fused with caustic potass, or treated 
with concentrated sulphuric acid, urea is re- 
solved into ammonia and carbonic acid. The 
same change takes place in the presence of de- 
composing animal matters as in stale urine, the 
urine becoming ammoniacal : — 

CO(H 2 N) 2 + 2H 2 - (NH 4 ) 2 C0 3 . 
Urea + aq. = ammonium carbonate. 

Uric acid, C5H4N4O3, is present in small 
quantities in the urine, in combination with a 
base. It is present in the spleen, liver, and 
also in the blood, in gout, and urinary calculi 
are often composed of it. It forms about 90 
per cent, of the solid residue of the urine of 



MEMOKANDA OF PHYSIOLOGY. O 

snakes, and is present in large proportion in the 
urine of birds. 

Preparation. — It is best obtained from the 
excrement of snakes, by boiling with caustic 
potass until the urate of ammonium of which it 
consists is decomposed, ammonia being evolved. 
The uric acid is precipitated in an impure state 
by adding hydrochloric acid. The precipitate 
is redissolved in potass and reprecipitated by. 
acid. 

From urine. — By acidulating with hydrochlo- 
ric acid, and allowing to stand for twenty-four 
hours, reddish crystals of impure uric acid 
being precipitated. 

Properties. — Pure uric acid is a white crystal- 
line powder, almost insoluble in cold water, 
insoluble in alcohol and ether. The crystals 
vary in shape, but are for the most part of a 
rhombic form. It is dibasic, and combines with 
bases to form soluble salts, as the urates of 
ammonium, potassium, and sodium. 

Tests — Murexide test. — A small portion of 
uric acid is moistened with strong nitric 
acid, and evaporated at a gentle heat. It 
effervesces, and leaves a reddish coloration, 
which on adding ammonia becomes purple. 
ScMjf*s Test. — Uric acid is dissolved in a solu- 
tion of sodium carbonate and dropped on 



b MEMORANDA OF PHYSIOLOOY. 

paper moistened with silver nitrate; a 
brown stain is formed. 

Santhin, C{>Il 4 N 4 0j, exists in small quanti- 
ties in urine, in the spleen, and muscles. It is 
insoluble in water, soluble in nitric and hydro- 
chloric acid. When heated with nitric acid and 
evaporated, a yellow residue is left. It occurs 
in some calculi. 

Hypoxanthin, Cr,H 4 N 4 0, occurs in the tis- 
sues of the spleen and muscles, and has been 
noticed in the urine of leukemia ; when oxi- 
dized it forms xanthin. 

Kippuric acid, C 9 HyN03, occurs in small 
quantities in the urine of man and carnivora, 
but abundantly in the urine of herbivora. It is 
precipitated by iron salts; most of its other 
salts are soluble. It crystallizes in fine needles. 

Kreatin, C 4 H a K 3 2 , exists in the muscles, 
and can be obtained from extract of meat. It 
occurs in colorless rhombic prisms. Soluble in 
hot, sparingly soluble in cold water. It has a 
neutral reaction, and when boiled with baryta 
water, splits up into urea and sarcosin. 

Kreatinin, C 4 H 7 N 3 0, is an alkaline body 
which exists in small quantities in muscle-ex- 
tract and in urine. It crystallizes in colorless 
prisms. Kreatin, on boiling' with HC1, takes 
up HoO and forms kreatinin. It can be sepa- 



MEMORANDA OF PHYSIOLOGY. 7 

rated from the urine by precipitating with mer- 
curic chloride. 

Lactic acid, C 3 H 6 3 , is the acid formed dur- 
ing lactic fermentation, and is found in sour 
milk and in the alimentary canal. Sarco-lactic 
acid has the same composition as lactic, but 
differs from it in the solubility and crystalline 
form of its zinc and calcium salts. It is found 
in the muscles, and can be obtained from mus- 
cle-extract. 

Cholesterin, C26H44O, is a neutral crystalline 
body (in reality an alcohol), which occurs in 
bile, in the brain, spinal cord, and many patho- 
logical fluids. It is readily prepared by boiling 
gall-stones in alcohol, filtering, and allowing to 
crystallize. With strong H 2 S0 4 , and a trace of 
iodine it becomes of a violet color, which after- 
ward changes to green and then red. 

Lecithin, C44H 90 NPO 3 , occurs in the brain, 
yolk of egg, pus, and in smaller quantities in 
the blood and bile. It is a white crystalline 
substance, soluble in hot alcohol and ether. 

Cerebrin and Neurin are two substances 
which occur in the brain, and the latter also in 
yolk of egg. 

Leucin, C 6 Hi 3 N0 2 , in conjunction with tyro- 
sin, is found in many of the organs and fluids 
of the body, in the pancreas, liver, spleen, in 



8 MEMORANDA OF PHYSIOLOGY. 

the peptones of the alimentary canal, and in 
the urine in acute yellow atrophy and other 
diseases of the liver. These substances are 
formed during the decomposition of albumi- 
nous substances. They may be prepared by the 
artificial decomposition of albumen, fibrin, 
casein, gelatin, &c, but are most readily ob- 
tained by boiling horn-chips in dilute sulphuric 
acid. Leucin can also be obtained syntheti- 
cally. Impure leucin appears under the micro- 
scope in the form of oily lumps clustering 
together ; when pure it forms white flat crys- 
tals. It is soluble in water and alkalies, less so 
in alcohol. 

Sclierefs Test, — Place a small portion on pla- 
tinum foil with a drop of nitric acid and 
evaporate gently. A colorless residue will be 
left, which, on the addition of liq. potassae, 
will become yellow and form an oily drop. 
Tyrosin, C 9 HiiN0 3 , is generally found in 
connection with leucin, and consists of minute 
colorless microscopic needles of a silky lustre. 
It is less soluble in water than leucin, and is in- 
soluble in alcohol, but soluble in liq. potassse 
and dilute acids. 

Hoffman* s Test. — Add mercuric nitrate and 
boil ; the liquids will become rose-colored 
and deposit a red precipitate. 



MEMORANDA OF PHYSIOLOGY. 9 

PiricPs Test. — Add a few drops of concen- 
trated sulphuric acid, warm, neutralize 
with chalk, filter, and add ferric chloride; 
the liquid will become of a violet color. 
III. Carbo-Hydrates. — The principal car- 
bo-hydrates found in the animal body are : 1. 
Grape sugar. 2. Milk sugar. 3. Inosit. 4. 
Glycogen. 5. Dextrin. 

1. Grape Sugar or Dextrose, C G H 12 G , oc- 
curs in small quantities in the blood and urine, 
and in larger quantities in the contents of the 
alimentary canal. It is formed in the mouth 
and intestines by the action of the saliva on 
the starch and cane sugar present in the food. 
When pure it forms four-sided prisms, but is 
generally seen in irregular warty lumps. It is 
soluble in water and alcohol. It undergoes de- 
composition in the presence of certain fer- 
ments. 

(a) Alcoholic fermentation takes place under 
the influence of yeast ; alcohol and carbonic 
acid are formed, 

C 6 H 12 O c = 2C 2 H 6 + 2C0 2 . 

(b) Lactic fermentation. — Under the influ- 
ence of decomposing animal matters, lactic acid 
is formed in the first instance and afterward 
butyric acid, carbonic acid and hydrogen. 



10 MEM0RA2O>A of physiology. 

1st stage, C 6 H 12 6 = 2C 3 H 6 3 

2d stage, 2C 3 H G 3 =C 4 H 8 2 + 2C0 2 + 2H 2 

The acidity of the contents of the large intes- 
tine is due to the presence of lactic acid. 

Trommels Test. — Boil the solution with a 
few drops of solution of cupric sulphate 
and excess of caustic potass ; if dextrose is 
present an abundant reddish-yellow precipi- 
tate of cuprous oxide will fall. 
Moore's Test. — Boil with caustic potass; if 
sugar is present the liquid will become first 
light yellow and afterward brown. 
Fermentation Test. — Add a small quantity of 
yeast, and leave in a warm place for twenty- 
four hours ; a considerable quantity of car- 
bonic acid will be evolved, which can be 
collected in a suitable apparatus. Alcohol 
will be present in the liquid. 

2. Milk Sugar or Lactose, C12H22O11, is 
found in milk. It differs from dextrose in be- 
ing more insoluble in water and not readily un- 
dergoing the alcoholic fermentation. It readily 
undergoes the lactic fermentation. It precipi- 
tates cuprous oxide from alkaline solutions in 
the same manner as dextrose. It is insoluble 
in alcohol. 

3. Inosit, CeHr^Ocj occurs in small quantities 



MEMORANDA OF PHYSIOLOGY. 11 

in the spleen, liver, and brain, and appears in 
the urine in uraemia. It undergoes the lactic 
but not the alcoholic fermentation. 

4. Glycogen, C 6 Hio0 5 , is found in consider- 
able quantities in the liver of well-fed animals, 
in smaller quantities in the white corpuscles of 
the blood, placenta, and foetal tissues. It is an 
amorphous, white tasteless powder soluble in 
water, insoluble in alcohol. Its aqueous solu- 
tion is opalescent. 

Preparation. — Kill a well-fed rabbit shortly 
after a meal, quickly remove the liver, and after 
cutting it in slices, throw it into boiling water 
without loss of time. After boiling for a short 
time (to prevent the ordinary post-mortem 
change which glycogen undergoes into grape su- 
gar), pound the liver, boil again and filter. The 
filtrate contains the glycogen and certain albu- 
minous substances which must be removed. 
The latter are precipitated with potassio-mer- 
curic iodide in the presence of hydrochloric acid. 
The glycogen is then precipitated by adding al- 
cohol. 

Tests. — Dilute mineral acids (except nitric) 
convert it into grape sugar. Iodine gives 
a red coloration, which disappears on warm- 
ing and reappears on cooling. {Starch gives 
blue with iodine, dextrin red, but disap- 



12 MEMORANDA OF PHYSIOLOGY. 

pears on warming, and does not reappear 
on cooling.) 

5. Dextrin, CgH 10 O 5 . — Starch is converted 
into dextrin by the action of ferments, the dex- 
trin formed being in turn converted into dex- 
trose if the action of the ferment is continuous. 
Dextrin is found in the alimentary canal and 
also in the blood. It becomes of a red color 
on addition of iodine ; the color disappears on 
warming, and does not, as in the case of glyco- 
gen, reappear on cooling. 

IV. Hydro-Carbons ob Fats. — The princi- 
pal fats present in the animal body are : 

Stearin ^ } 3 
Palmitia . ( gS, i0) , \0. 

0lehx (c; H rLo)3 }° 3 

These neutral fats, when submitted to the ac- 
tion of superheated steam, or heated with lead 
oxide, combine with water, and form glycerine 
and a fatty acid. 

Palmitin. Glycerine. Palmitic acid. 

C3H5 ^ ~ _j_a^- In — ^3^5 ) /-) 1 qC I6 H 31 0q 
(C 16 H 31 0) 3 j °s + d H f ° ~ H 3 f° 3 + d H °" 



MEMORANDA OF PHYSIOLOGY. 



13 



Stearin is best obtained from beef or mutton 
suet. It is the hardest of the fats, and crys- 
tallizes in white shining plates. It has the 
highest melting point (60° C.) 

Palmitin is best prepared from palm oil ; it 
crystallizes in needles and has a lower melting 
point than stearin (40° C.) 

Olein is prepared from olive oil, and is fluid 
at ordinary temperatures. 

TT \ 

Glycerine, C 3 tt 5 [ 3 , is a syrupy fluid with 

sweet taste and a neutral reaction ; it is soluble 
in water and alcohol, but not in ether. It dis- 
solves many metallic oxides, and on heating 
decomposes, acrolein being formed. 

V. The Albuminous Bodies or Proteids 
occur in almost all the tissues and fluids of the 
body. They derive their name from the white 
of egg, which is taken as a type of the group. 
They will not crystallize, and are obtained pure 
with difficulty. They are insoluble in alcohol 
and ether, soluble in strong acids and alkalies, 
undergoing decomposition in the process. With 
the exception of the peptones they are coagu- 
lated by heat, and will not diffuse through ani- 
mal membranes. They are not formed in the 
animal body, but enter the body in the form of 
food derived from the vegetable kingdom. They 



14 MEMORANDA OF PHYSIOLOGY. 

have \he following average percentage compo- 
sition : 

21 per cent. 

H 7.5 " " 

C 54 « " 

N 16 " H 

S 1 " « 

Tests. — 1. Xantlwprolein Reaction. — Heat 
with strong nitric acid, cool, and add am- 
monia. An orange color is produced. 

2. Milton's Reaction.— Add some Millon's re- 
agent (Hg(N0 3 ) 2 + HgN0 3 ) and heat ; the 
fluid will become red, and if sufficient albu- 
men is present, a precipitate will fall. 

3. Add some liq. potassae and a drop or two 
of solution of cupric sulphate ; heat : a vio- 
let color is produced. 

The albuminous bodies include several groups : 

1. Albumen and its derivatives, 

2. Globulins. 3. Fibrin. 4. Peptones. 

1. Albumen is soluble in water, insoluble in 
alcohol and ether. It is coagulated at a tem- 
perature of 70° 0. If dried at a lower tempera- 
ture, it forms a tasteless yellow mass. Albumen 
is precipitated in the following ways : — 



MEMORANDA OF PHYSIOLOGY. Ii> 

(a) By boiling and acidulating with nitric 

acid. 

(b) By concentrated nitric acid in the cold. 

(c) By the addition of acetic acid and potassic 

ferrocyanide. 

(d) Boiling with acetic acid and strong solu- 

tion of sodium sulphat 

Albumen exists in two forms — egg albumen 
and serum albumen. 
They differ in that— 

(a) Egg albumen is coagulated by ether, serum 

albumen is not. 

(b) Coagulated serum albumen is soluble in 

strong HN0 3 , egg albumen is not. 

(c) Serum albumen injected beneath the skin 

does not appear in the urine, egg albumen 
does. 

Alkali Albuminate. — If albumen in solution 
is treated with dilute caustic potash and gently 
warmed, some of its properties undergo change. 
The alkaline solution will no longer be precipi- 
tated by boiling. It is precipitated on neutral- 
ization with acids, and is soluble in excess of the 
acid. It is not precipitated on neutralization 
in presence of the alkaline phosphates. 

Casein. — This substance closely resembles 
alkali albuminate, but differs from it in con- 



13 MEMOKANDA OF PHYSIOLOGY. 

taining sulphur. It can readily be prepared 
from milk by saturating with magnesium sul- 
phate, or by acidifying and gently warming ; ife 
is precipitated when milk comes in contact with 
the walls of the stomach. 

Acid Albumen. — If albumen in solution is 
treated with HC1 or other acids, it undergoes a 
change iu its properties. It is no longer coagu- 
lated by heat. It is precipitated on neutraliza- 
tion with an alkali, and is redissolved by excess : 
its precipitation is not prevented by alkaline 
phosphates. It is precipitated on boiling with 
lime-water. If muscle be dissolved in dilate 
HC1, a body termed syntonin, closely resembling, 
if not identical with, acid albumen, is formed. 

2. Globulins. — These bodies differ from the 
albumens in being insoluble in water, precipi- 
tated by C0 2 , or on saturating their solutions 
with NaCl. They are converted into acid albu- 
men by HC1. They are soluble in dilute solu- 
tions of NaCl, the solution being precipitated by 
heat. 

They include (a) globulin, (b) paraglobulin, 
(c) fibrinogen, (d) myosin, (e) vitellin. 

(a) Globulin exists in the crystalline lens, 
and closely resembles paraglobulin in its prop- 
erties, but differs from it in not assisting to form 
fibrin. 



MEMORANDA OF PHYSIOLOGY. 17 

(b) Paraglobulin occurs in blood and serum, 
and in smaller quantities in some of the tissues. 
It gives rise to fibrin when mixed with any fluid, 
as hydrocele fluid, containing fibrinogen. 

(c) Fibrinogen exists in blood, pericardial, 
pleural, and hydrocele fluids. It closely re- 
sembles paraglobulin, but when thrown down 
by C0 2 it is less flocculent and more viscous. 

(d) Myosin is present in dead muscle. It is 
not so soluble as fibrinoplastin. It is converted 
into syntonin by dissolving in HC1. 

(e) Vitellin exists in yolk of egg ; it is solu- 
ble in dilute NaCl solutions, but differs from 
other members of the group in not being pre- 
cipitated by saturating with NaCl. 

8. Fibrin is obtained by whipping freshly 
drawn blood. It forms tough, white strings, 
which are insoluble in water and dilute NaCl 
solutions ; is converted into syntonin by diges- 
tion with HC1. 

4. Peptones are distinguished from other 
albuminous bodies by not being precipitated by 
boiling, acids, or by potass, ferrocyanide and 
acetic acid. They diffuse through animal mem- 
branes. They are precipitated by tannin, 
iodine, and acetate of lead. 

Several different peptones exist. 

VI. The Albuminoids ok Gelatinous 
2 



18 MEMORANDA OF PHYSIOLOGY. 

Bodies. — These substances, which occur as the 
principal constituents of many tissues, resemble 
the albuminous bodies in their composition, but 
differ from them in many of their reactions. 

They include — 

1. Mucin. 3. Chondrin. 

2. Gelatin. 4. Elastin. 

1. Mucin is found in foetal connective tissue 
and in tendons. It occurs also in the mucous 
secretions, saliva, bile, gastric juice, etc., giv- 
ing them their ropy consistence. It is not 
coagulated by boiling. It is precipitated by 
acetic acid. It gives the proteid action with 
Millon's reagent and nitric acid, but not with 
sulphate of copper and liq. potass. 

2. Gelatin. — Bones, connective tissues, ten- 
dons, yield gelatin on boiling. When dry it is a 
colorless, transparent body ; it swells up in cold, 
and dissolves in hot water; the solution, on 
cooling, forms a jelly. It is precipitated by 
tannic acid and mercuric chloride, not by acetic 
acid. It does not yield the proteid reactions 
with nitric acid, Millon's reagent, or copper sul- 
phate. 

3. Chondrin forms the bulk of the matrix cf 
cartilage, and can be prepared by boiling car- 
tilaginous substances in water, the solutions 



MEMOKANDA OF PHYSIOLOGY. 



19 



forming a jelly on cooling. It is precipitated 
by acetic acid and lead acetate. 

4. Blastin, — The yellow elastic fibres pres- 
ent in the liq. subflava, and other parts of the 
body, consist of elastin. It does not dissolve in 
boiling water, but is soluble in boiling caustic 



Section 2. 
PHYSIOLOGICAL HISTOLOGY. 

EPITHELIUM. 

The various free surfaces of the body — as, for 
example, the external surface of the skin, the 
mucous membranes, the internal membrane of 
the arteries, and the serous sacs — are lined by 
cells of different characters, which form the 
epithelium or endothelium. The latter term is 
applied by some to the flattened cells which 
line the serous sacs, blood-vessels, and lym- 
phatics. 

The epithelial cells differ very considerably in 
shape and size, but they agree in possessing" 
nuclei and finely granular cell-contents. This 
granular protoplasm has recently been shown 
to consist of a fine network, the meshes of 
which contain a hyaline material. The nucleus 
in like manner consists of a fine network, hya- 
line material, and has also a limiting membrane 
(Klein). Epithelial cells are connected together 



MEMORANDA OF PHYSIOLOGY. 21 

by a small quantity of a homogeneous albumi- 
nous substance, which is termed the intercellu- 
lar cement. 

Epithelium may be divided into the following' 
varieties : — 

1. Tessellated or squamous. 

2. Columnar. 

3. Transitional. 

4. Glandular. 

5. Ciliated. 

1. The Tessellated or Squamous variety is 
arranged either as a (a) single layer, or (b) in 
superimposed or stratified layers. 

(a) A single layer of tessellated epithelium is 
found lining the pleura, pericardium, perito- 
neum, arachnoid, arteries, veins, capillaries, 
lymphatic vessels, acini of the lungs, anterior 
and posterior aqueous chambers of the eye. 
The cells consist of a thin plate with an oval 
nucleus, but differ considerably in shape ; those 
lining the serous sacs being polyhedral or nearly 
circular, the cells lining the arteries and capil- 
laries being elongated, and the lymphatics hav- 
ing epithelium, with an irregular or wavy bor- 
der. The outline of these cells is readily shown 
by staining their intercellular cement with silver 
nitrate. 



22 MEMOKANDA OF PHYSIOLOGY. 

(b) The superimposed layers consist of strata 
of cells, which clothe surfaces specially liable 
to friction. They cover the true skin, forming 
the epidermis ; they form the superficial layer 
of the mucous membrane of the cavity of the 
mouth, tongue, oesophagus, conjunctiva, and 
vocal cords, vagina, external aperture and fossae 
navicularis of the urethra. The deeper cells of 
the dermis are more or less round, though the 
deepest are columnar, and form the rete mueo- 
sum ; the superficial cells are flattened, forming 
the horny layer or stratum corneum, which 
covers the soles of the feet and palms of the 
hand. 

2. Columnar. — This variety consists of cylin- 
drical or club-shaped nucleated cells, the thick 
ends being toward the free surface. They are 
found lining the alimentary canal from the 
oesophageal end of the stomach to the anus, 
lining the ducts of glands and the olfactory 
region of the nose. 

3. Transitional. — This variety consists of flat- 
tened cells on the surface, a middle layer of 
pear-shaped cells, their rounded ends fitting 
into the under surface of the flattened cells, 
and an inferior layer of rounded or pyriform 
cells fitting between the thin ends of the middle 
layer. The bladder, ureters, pelvis of kidney, 



MEMORANDA OF PHYSIOLOGY. 23 

are lined by transitional epithelium, and also 
the larynx and pharynx, where the columnar 
and flattened cells come in contact. 

4. Glandular. — The acini of the various 
glands of the body, as the convoluted tubes of 
the kidney, the salivary and peptic glands, are 
lined by spheroidal or cubical cells. These cells 
are nucleated, and probably perform the im- 
portant work of separating or elaborating from 
the blood the materials which form the secre- 
tion of the gland. 

5. Ciliated. — In some parts of the body the 
epithelial cells are provided with minute rods, 
which are constantly in motion and serve to 

. propel mucus or any minute 'particles in contact 
with them toward the orifice of the chamber 
or tubes whose walls they line. They vibrate 
at the rate of about 700 per minute. These 
minute rods are probably prolongations of the 
intra-cellular network, and their movements are 
independent of any nervous mechanism. Chlo- 
roform vapor and carbonic acid gas arrest their 
movements. Weak acids or alkalies and moder- 
ate electric currents stimulate them. Ciliated 
epithelium is for the most part columnar in 
shape . 

They are present in man — 

(a) Lining the mucous membrane of the air- 



24 MEMORANDA OF PHYSIOLOGY. 

passages. Commencing 1 near the nostrils, they 
line the nasal cavity (except the olfactory re- 
gion), the antrum, ethmoidal and frontal sin- 
uses, the nasal and lachrymal ducts, the upper 
part of the pharynx, the Eustachian tube, tym- 
panic cavity, trachea, and bronchi, till they 
enter the inf undibula of the lungs. 

(b) Lining the mucous membrane of the ute- 
rus, commencing at the middle of the cervix 
and continuing along the Fallopian tubes to 
their fimbriated extremities. 

(c) Lining the vasa efferentia, coni vasculosis 
and upper part of the globus major of the testis. 

(d) Lining the lateral ventricles of the brain 
and central canal of the spinal cord in the child. 

Many of the animalcule and algas, as the par- 
amecia, rotifera, vorticella, volvox, are pro- 
vided with cilia as a means of locomotion, or for 
producing currents in the water, so as to carry 
their prey within their reach. Cilia are also 
found in the gills of the oyster and salt-water 
mussel, and doubtless serve to bring a fresh 
supply of oxygenated water in contact with the 
capillaries of their gills. In man, they prob- 
ably prevent the accumulation of mucous or 
foreign particles on the surfaces they line, and 
possibly in the testicle help forward the imma- 
ture spermatozoa. 



MEMORANDA OF PHYSIOLOGY. 25 

They are most readily obtained for the micro- 
scope by snipping a small piece from the gills 
of the oyster or the mussel, and covering with 
thin glass ; they will continue to work for hours 
if evaporation be prevented. 

PIGMENT. 

Pigment is met with in various parts of the 
body, in the choroid, iris, olfactory region of the 
nose, pia mater of the chord, and in some of the 
cells of the gray matter of the brain. It occurs 
in some pathological states, as in the rete mu- 
cosum in Addison's disease, and in melanotic 
tumors. 

The choroid contains hexagonal cells filled 
with dark matter ; on the outer surface of the 
choroid the cells are branched. The pigment of 
the choroid is evidently of use in absorbing any 
redundant light which enters the eye. Chemi- 
cally it is characterized by the large percentage 
(nearly sixty per cent. ) of carbon which it con- 
tains. 

CONNECTIVE TISSUE. 

Connective Tissue is present almost uni- 
versally throughout the body, serving to connect 
the various organs with one another, as well as 



26 MEMOKANDA OF PHYSIOLOGY. 

to bind together the parts of which an organ 
consists. The muscles are surrounded by a con- 
nective tissue sheath, which also penetrates into 
their substance, binding together the fasciculi 
and fibres. The same tissue is present beneath 
the skin and mucous membranes, and forms a 
sheath for the arteries, veins, and nerves. It is 
plentifully supplied with blood-vessels, and 
many nerves pass through its substance. Mi- 
croscopically, three different elements may be 
seen — 

1. Corpuscles and nuclei. 

2. White fibrous tissue. 

3. Yellow fibrous tissue. 

1. Corpuscles.- — These are most readily seen 
in the subcutaneous tissues of young animals, 
as in the young of the guinea-pig. Besides the 
fibres, irregular-shaped nucleated cells will be 
seen. Many of the cells are branched, the 
branches anastomosing with one another. These 
cells occupy spaces which they completely fill. 
There is a certain amount of finely granular 
material between the cells and fibres, which 
stains with nitrate of silver, the cells and fibres 
being unstained. The nuclei readily stain with 
carmine, while the fibres do not. 

2. White Fibrous Tissue forms the major 



MEMORANDA OF PHYSIOLOGY. 27 

part of the connective tissue of the body. Mi- 
croscopically, it consists of white, wavy paral- 
lel fibres, which swell up on the addition of 
acetic acid. On boiling-, it yields gelatine. 

3. Yellow Fibrous Tissue forms a variable 
proportion of connective tissue, being especially 
abundant beneath the skin, mucous and serous 
membranes. Microscopically, it consists of yel- 
low, elastic, curling-, branching fibres, of a 
larger size than the fibres of white fibrous 
tissue. It is unchanged by acetic acid and the 
weaker alkalies. Chemically, it yields elastin. 

Distribution of White Fibrous Tissue.— 
Those connecting tissues of the body which 
require to be inelastic, tough, unyielding, are 
formed of pure white fibrous tissue, without 
admixture of yellow. Such are the tendons, 
f ascias, aponeuroses, most ligaments, the perios- 
teum, the dura mater, pericardium, etc. They 
are white in color, and will not readily stretch. 
Besides the ordinary wavy fibres, they contain 
connective tissue corpuscles. 

Distribution of Yellow Elastic. — In some 
parts of the body an elastic material is required 
to connect bones together or to form the walls 
of blood-vessels. Yellow elastic tissue enters 
largely into the following structures : — 

1. Ligamenta subflava of the vertebrae. 



28 MEMORANDA OF PHYSIOLOGY. 

2. The stylohyoid, thyro-hyoid, crico-thyroid 

ligaments, the vocal cords, and ealcaneo- 
scaphoid ligament. 

3. The middle coat of the larger arteries and 

veins. 

4. It is present beneath the mucous mem- 

brane of the trachea, and forms the walls 
of the infundibula. 

5. The capsule and trabecule of the spleen, 

lymphatic glands, and erectile tissues. 

6. forming the ligamentum nuchas of horse 

and ox. 

RETIFORM TISSUE. 

Retiform Tissue consists of a delicate net- 
work formed by connective tissue corpuscles 
joining their branches together. In some parts 
the corpuscles and their nuclei are very appar- 
ent, whilst elsewhere but little can be seen of 
nuclei at the intersections of the fibres. Reti- 
form tissue forms the stroma or framework of 
lymphoid tissue. 

In lymphoid tissue, the spaces in the network 
are occupied by leucocytes. It is found in lym- 
phatic glands, solitary glands of the intestine, 
tonsils, spleen, etc. 



MEMORANDA OF PHYSIOLOGY. 29 



ADIPOSE TISSUE. 

Adipose Tissue is present in many parts of 
the body. It forms a layer beneath the skin, 
in the subcutaneous connective tissues, except 
beneath the skin of the eyelids and penis ; it 
forms a layer of considerable thickness covering 
the buttocks, thighs, and abdomen, in well- 
nourished subjects. In the internal organs it is 
collected around the kidneys, heart, and folds 
of the omentum, but it is absent from the cra- 
nium and lungs. 

Structure. — Beneath the microscope, adipose 
tissue will be seen to consist of small vesicles, 
3oo to 5-io inch in diameter, with a delicate 
envelope containing yellow oily matters. These 
vesicles are held together and supported by 
connective tissue, and are plentifully sup- 
plied' with blood-vessels. A nucleus is some- 
times to be seen, though often obscured by the 
fatty matters. In prepared specimens, crystals, 
probably of palmitic acid, may be seen occupy- 
ing the vesicles. The contents of the vesicles 
in the human body consist of olein, palmitin, 
and stearin. 

Uses. — 1. Adipose tissue serves as a conveni- 
ent packing material, which fits in between the 



30 MEMORANDA OF PHYSIOLOGY. 

tissues and organs, and from its fatty nature it 
serves to diminish friction. For example, the 
subcutaneous fat covering- the buttock, will form 
a soft pad, and allow the skin to work smoothly 
over subjacent structures. 

2. Adipose tissue is an excellent non-conduc- 
tor, and serves to retain the heat of the body. 

3. Adipose tissue serves to store up for future 
use a substance rich in carbon and hydrogen. 
The destiny of fat is eventually to be converted 
into C0 2 and H 2 0, its oxidation serving to main- 
tain the heat of the body and give rise to mus- 
cular energy. Hybernating animals fatten dur- 
ing the autumn on starchy foods, the stored fat 
serving to maintain them during their winter 
sleep. 

CARTILAGE. 

Cartilage is a bluish or yellowish white, 
semi-translucent elastic substance, without ves- 
sels or nerves, and surrounded by a fibrous 
membrane, the perichondrium. Cartilage, on 
boiling for some hours, yields an albuminoid 
called chondrin, which, like gelatin, sets into a 
jelly on cooling, but differs from gelatin in being 
thrown down by tannic acid. 



MEMORANDA OF PHYSIOLOGY. 31 

Cartilage may be divided into 

f Temporary, 
1. Hyaline -i Costal, 

I Articular. 



2. Fibro-cartilage j 



White, 
Yellow. 



1. Hyaline Cartilage is present in many 
parts of the body. In the f cetus it forms a firm, 
elastic material for the skeleton, prior to the 
deposition of lime salts and consolidation of the 
bones. In the adult it supplies an elastic ma- 
terial in the costal cartilages, to assist in form- 
ing the walls of the chest, its elasticity aiding 
in an important manner the expiratory act. Ifc 
caps the ends of bones at the joints, and helps 
to diminish friction and lessen shock. It forms 
in large measure the walls of the trachea and 
bronchi, serving to maintain their rigidity and 
prevent collapse. 

Structure. — It presents beneath the micro- 
scope numerous round or angular nucleated 
cel]s scattered through a finely granular matrix. 
The cells lie in a cavity of the matrix, the 
cavity being lined by a capsule. 

Hyaline cartilage is modified in different sit- 
uations : — 

(a) Temporary. — Cartilage forms a support 






32 MEMOEANDA OF PHYSIOLOGY. 

for the foetus, and a bed for the deposition of 
the lime salts. The cells are small, for the most 
part angular, provided with tails, and uniformly 
scattered through the matrix, except where 
ossification is proceeding, when they arrange 
themselves in columns. The matrix is very 
finely granular. 

{b) Costal. — The cells are large and collected 
into groups, and contain oil globules. The ma- 
trix exhibits a tendency to the deposition of 
lime salts, though no true bone is formed. The 
matrix contains some scattered fibres. 

The cartilages of the nose, thyroid, cricoid, 
trachea, and bronchi, resemble costal, though 
for the most part no fibres are to be seen in the 
matrix. 

(c) Articular. — The cells near the bone are 
arranged in columns, though irregularly distrib- 
uted near the surface. The matrix is not prone 
to calcify. 

FIBRO-CARTILAGE. 

1. White fibro-cartilage. 

2. Yellow fibro-cartilage. 

White Fibro-cartilage differs from hyaline 
in having the matrix occupied by fibres of white 
fibrous tissue. It is consequently tougher and 



MEMOEANDA OF PHYSIOLOGY. 33 

less elastic. Its microscopic characters resemble 
white fibrous tissue rather than cartilage, con- 
sisting of parallel wavy fibres with a few carti- 
lage cells. It is distributed in the following 
manner : — 

1. Inter-articular fibro-cartilages form small 
pads occupying a movable joint, their surfaces 
being free and lined by synovial membrane. 
They greatly assist in deadening the effects of 
shock. They are present in the temporo-max- 
illary, sterno-clavicular, acromio-clavicular, in- 
ferior radio- ulnar articulations, and also in the 
knee-joint. 

2. Circumferential, serving to deepen articular 
cavities, as in the glenoid canities of the shoulder 
and hip -joints. 

3. Connecting, which serve to connect the sur- 
faces of bones together in immovable joints, and 
at the same time to diminish shock — as the in- 
tervertebral disks, sacro-iliad synchondrosis. 

4. Lining Bony Grooves, serving to deepen 
and render smooth the grooves in which certain 
tendons work, as the tendons of the peronei, ex- 
tensors of the thumb. 

Also forming the sesamoid cartilages devel- 
oped in several tendons. 

Yellow Elastic Fibre-cartilage differs from 
hyaline in having its matrix pervaded with yellow 



34 MEMORANDA OF PHYSIOLOGY. 

elastic tissue. It is tougher, more flexible and 
elastic than the hyaline variety. Microscopical 
examination of the epiglottis shows a fine net- 
work of elastic fibres, with numerous cartilage- 
cells scattered through its substance. In the 
external ear the network of elastic fibres are 
coarser. It forms the Eustachian tube, external 
ear, epiglottis, and cornicula laryngis. 

BONE. 

Bone is a tough, hard, white substance, which 
forms the skeleton of the adult. It is also elas- 
tic, as seen in the clavicle and ribs. It consists 
of two different kinds of material, compact and 
cancellous tissue. The compact, as its name im- 
plies, is dense and hard, and forms the outer 
shell of bone. Cancellous tissue occupies the 
internal parts, and consists of spicules of bone, 
forming a network, and leaving spaces filled with 
fatty matters and blood-vessels. The two tissues 
gradually shade off into one another, there being 
no well-marked separation between them. Bone 
is surrounded by a fibrous membrane, the perios- 
teum, which supports the blood-vessels. Its 
outer layer is formed of tough fibrous tissue, its 
inner layers of fine elastic fibres, and in young 
growing bone of numerous corpuscles and gran- 



MEMORANDA OF PHYSIOLOGY. 35 

ular matter. The long bones consist of a zone 
of compact tissue on the surface, an inner zone 
of cancellated tissue, and a medulla filled with 
marrow in the centre. The marrow in adults 
consists largely of fatty matters, with a certain 
number of nucleated cells resembling leucocytes, 
extractives, and salts. The red marrow of young 
bones is formed largely of cellular elements and 
but little fat. 

Chemical Composition : 

Animal matter 33.3 

Mineral * fc 66.7 

The animal matter is converted by boiling into 
gelatin. 

The mineral consists of calcic phosphate, 
calcic carb., magnesia, sodium, fluorides and 
chlorides. 

Minute Structure. 

1. Haversian canals. 

2. Lacunae, canaliculi, osteo-blasts. 

3. LamellaB and perforating fibres. 

On examining with a low power a thin trans- 
verse section of a long bone (which has been 
ground extremely thin or decalcified and a sec- 
tion cut), a number of dark spots, or round 



36 MEMORANDA OF PHYSIOLOGY. 

apertures, will be seen, from ^ou^h to ; i *o uth of 
an inch in diameter. They are transparent or 
dark, according as the bone has been prepared 
by cutting" or grinding. They are the apertures 
seen in section of the Haversian canals, and are 
occupied by blood-vessels. The lacunae will be 
seen as small, elongated, dark bodies arranged 
concentrically around the Haversian canals, and 
on examining with a higher power, will be seen 
to have numerous fine lines, in reality fine tubes 
or pores, radiating from them : these are the 
canaliculi. The lacunae are small spaces oc- 
cupied by a nuclear cell, called an osteo-blast, 
which influences the nutritive processes going 
on in the bone. The canaliculi communicate, 
on the one hand, with the Haversian canals, 
and, on the other, with the lacunas, and are the 
means of conveying nutritive material from the 
blood-vessels to the osteo-blasts. In addition to 
the lacunae, numerous concentric rings will be 
seen surrounding each aperture of the Haver- 
sian canals. These rings are occasioned by the 
transverse section of cylinders or layers of bony 
tissue surrounding the Haversian canals. In 
addition to the lamellae around the canals, there 
are other lamellae arranged concentrically around 
the medullary cavity of the bone. If a very 
thin shred of a lamella be examined by a high 



MEMORANDA OF PHYSIOLOGY. 37 

power, it will be seen to consist of an exceed- 
ingly fine intersection of fibres, which cross one 
another obliquely, and cannot be readily teased 
out. The lamellge also exhibit numerous per- 
forations, one set corresponding to the canal- 
iculi, another set, larger and fewer in number, 
corresponding to the 'perforating fibres which 
piece adjacent lamella in perpendicular and ob- 
lique directions, and bolt them together. 

Ossification in Membrane. — The roof of the 
skull is ossified from membrane, i. e, the parie- 
tal, greater part of the frontal, part of occipital, 
sphenoid, and temporal, and some of the smaller 
bones. The base is formed from cartilage. 
Growth of bone takes place by the ossification 
of the inner layer of the periosteum. When 
the tissue in which ossification is proceeding is 
examined by a high power, it appears to be 
made up of fibres and corpuscles, with fine gran- 
ular uniting matter. The corpuscles are large 
and granular, with well-marked nuclei. Ossifi- 
cation proceeds by a deposit of lime-salts in 
the finely granular uniting material surround- 
ing the corpuscles, the spaces occupied by the 
corpuscles forming the lacunse, and the blood- 
vessels imprisoned in a similar manner forming 
the Haversian canals. 

Ossification in Cartilage. — In a long bone 



38 MEMOKANDA OF PHYSIOLOGY. 

ossification begins in the centre, and afterwards 
separate centres appear, forming the epiphyses 
which subsequently join the shaft. 

On examining a longitudinal section of bone 
undergoing ossification, it will be found that 
the first indication of the commencing process 
is, that the cartilage cells, at first scattered 
irregularly through the matrix, begin to ar- 
range themselves in columns parallel to the long 
axis of the bone. Blood-vessels shoot up in 
loops between these columns, and lime-salts are 
poured out and precipitated in the matrix. As 
the deposit of lime proceeds it shuts in por- 
tions of the columns of cells and forms short 
fusiform spaces. The cartilage cells impris- 
oned within the fusiform cavities disappear, 
and the cavities become lined by corpuscles 
similar to those seen in intra-membranous ossi= 
fication. These corpuscles are either descend- 
ants of the cartilage -cells, or are leucocytes 
derived from the blood. The first bone formed 
is very vascular, and consists of fusiform spaces 
with bony walls, and filled in part with large 
granular cells. These spaces soon communicate 
with one another, and a tissue resembling can- 
cellous tissue is produced. Finally, part of 
this newly formed tissue disappears to form the 
medullary cavity, and part remains to form 



MEMOKANDA OF PHYSIOLOGY. 39 

cancellous tissue, while osteo-blasts, or cor- 
puscles, lining the spaces become imbedded in 
calcined material forming the compact tissue, 
which is also formed, as the bone grows, by 
the ossification of the inner layer of the perios- 
teum. 

MUSCLE. 

There are two varieties of muscular tissue in 
the body. 

I. Striated muscular fibres. 
II. Non-striated muscular fibre. 

I. Striated Muscular Fibre is found in the 
muscles attached to bone, such as the biceps, 
diaphragm, masseter, also in muscles of tongue, 
soft palate. pharyn«, larynx, upper part of 
oesophagus, platysma, sphincter vesicas, muscles 
of prostate. For the most part muscles, which 
are under the control of the will, are striated, 
though exceptions are found in the constrictors 
of the pharynx, oesophagus,- heart, &c. Striped 
muscle is of a dull red color, and marked with 
longitudinal furrows on its surface. 

A voluntary muscle consists of 

1. Connective, tissue sheath. 

2. Fasciculi. 

3. Fibres and sarcolemma. 

4. Discs, fibrillse and sarcous elements. 






40 MEMORANDA OF PHYSIOLOGY. 

1. Sheath. — Each muscle has its sheath of 
connective tissue which surrounds it and binds 
the fasciculi together, and is called the peri- 
mysium ; it sends fine prolongations in between 
the fibres called the endomysium. 

2. Fasciculi. — The longitudinal furrows seen 
on the surface of the muscle, when the sheath 
is removed, divide the surface into divisions 
called the fasciculi. These divisions are coarse 
in the gluteus maximus, deltoid, and other 
powerful muscles, while others, as the facial 
muscles, have fine fasciculi. 

3. Fibres — The fibres may readily be seen 
by teasing out a piece of muscle (which has 
been macerated in alcohol or ammonium bi 
chromate) under a low power. They are pris 
matic in section, from -±qtj to T £u in. diameter, 
and are marked transversely with dark stride, 
close together, and at regular intervals. Oval 
elongated nuclei are seen in the fresh muscle of 
the frog when treated with acetic acid. They 
are also present in mammalian muscles, being 
situated near the surface of the fibres, beneath 
the sarcolemma. 

Sarcolemma. — The fibres are surrounded by 
a delicate homogeneous elastic sheath, which 
can be readily seen in prepared muscle of frog 
and water-beetle, less readily in man, called the 



HEMOKANDA OF PHYSIOLOGY. 41 

sarcolemma ; under favorable circumstances 
transverse membranous septa will be seen, 
which are connected with the sarcolemma and 
cross the fibre in the intervals between the dark 
striae, dividing the muscle into compartments 
(each containing a disc), called Krause's mem- 
branes. 

4. Discs. — If the living muscle of the water- 
beetle (Hydrophilus) be examined under a high 
power, the appearance of transverse strijB will 
be seen to be due to alternate dark and clear 
discs, the former "highly refractive, the latter 
less so. The dark strias form the contractile 
discs, the light the interstitial discs, the latter 
taking no part in the contraction of the muscle. 
A contractile disc occupies one of the compart- 
ments formed by Krause's membranes. 

Fibrillae and Sarcous Elements. — If muscle 
be examined after death, especially if it has 
been soaked in alcohol or chromic acid, the fibres 
will be seen to be split up longitudinally into 
smaller fibres or fibrillas, and these again di- 
vide transversely so as to form minute bodies, 
the sarcous elements of Bowman. 

Schafer has described in the muscle-fibres of 
the water-beetle the dark cross strias, or the con- 
tractile discs mentioned above, to consist of 
minute rods arranged side by side in the long 



42 MEMORANDA OF PHYSIOLOGY. 

axis of the fibre, their ends being enlarged into 
minute knobs. 

Cardiac Muscular Fibre differs -from ordi- 
nary striated muscle in having very faint cross 
stripes and no sarcolemma ; the fibres are also 
branched. If the fibres are acted on by osmic 
acid, they are seen to consist (in mammals) of 
oblong nucleated cells, some being forked at 
their extremities, and joined end to end. 

II. Non-Striated Muscular Fibre is pale in 
color, is not under voluntary control, and con- 
sists of bundles of contractile cells. It is found 
in many parts of the body — walls of stomach 
and intestines, blood-vessels, trachea, oesopha- 
gus, ducts, iris, etc. The cells are elongated or 
spindle-shaped, with an oblong rod-shaped 
nucleus. They vary in length, and are Yom 
in. to seta© m - m breadth. The cells are held 
together by a transparent semi-fluid cement 
substance. 

Properties of Muscular Tissue. 

Chemical. — If living contractile muscle of 
frog be freed from blood, and subjected to com- 
pression, or frozen and pounded with snow con- 
taining one per cent, of salt, a fluid termed 
muscle-plasma is obtained, which, like blood, 



MEMORANDA OF PHYSIOLOGY. 43 

coagulates into clot and serum. The clot, which 
is granular and flocculent, is myosin, and the 
serum contains albuminates, and nitrogenous 
principles, as kreatine, xanthine, etc. , also sarco- 
lactic acid, inosite, glycogen, and salts. Myosin 
resembles globulin in many respects ; it is con- 
verted into syntonin or acid albumen by the 
action of acids, and into alkali albumen by 
alkalies. Dead muscle contains myosin, which 
can be dissolved out by a ten per cent, solu- 
tion of sodium-chloride. Living muscle con- 
tains no myosin, but substances which are 
converted into myosin at the death of the 
muscle. Living muscle is alkaline or neutral ; 
dead muscle is acid from formation of sarco- 
lactic acid. Living muscle contains glycogen, 
which, at its death, is converted into sugar. 

Electrical muscle- currents. — Living muscle, 
like nerve, is traversed by electrical currents. 
If a piece of living muscle be placed upon elec- 
trodes (non-polarizable, i. e. , so arranged as to 
prevent the electrodes themselves from develop- 
ing currents when in contact with the muscle), 
connected with a delicate galvanometer, it will 
be noticed that an electrical current passes 
through the galvanometer from the equator or 
some point on the surface of the muscle to the 
cut end ; the greatest deflection taking place 



44 MEMORANDA OF PHYSIOLOGY. 

when the electrodes are placed one at the mid- 
point of the surface and the other at the cut end. 
A current will pass in the opposite direction 
from the cut end to the mid -point in the muscle. 
The current ceases as the muscle dies. 

Contractility. — Both muscle and nerve in a 
living state are irritable, that is, they respond 
when a stimulus is applied. The muscle re- 
sponds by contracting, the nerve by transmitting 
the stimulus to its termination. Tnis contrac- 
tility is the characteristic property of muscle. 
If a muscle of a recently killed frog be laid bare, 
and any form of stimulus applied, such as the 
electrodes of a battery or coil, a hot wire, a 
chemical substance, or a mechanical injury, it 
will be thrown into a state of contraction. The 
stimulus may be applied to muscle itself, or to 
a nerve in connection with the muscle. 

If the electrodes of an induction coil be laid 
on the sciatic nerve of a frog, and a single in- 
duction-shock (either making or breaking) be 
made, the gastrocnemius will give a short sharp 
contraction. If the muscle be attached to a 
lever arranged to record its movements on a re- 
volving drum, a curve will be produced, the 
lever rising during contraction and falling dur- 
ing relaxation. The figure traced is the muscle 
curve. The time occupied in tracing the curve 



MEMOKAKDA OF PHYSIOLOGY. 45 

can be measured by a marker in contact with a 
drum, transmitting the vibrations of a tuning- 
fork. With a suitable arrangement of the above 
apparatus, the curve will demonstrate three 
facts : 

1. The "latent-period" — i.e., a short time, 
say -Vth second elapsing after the entrance of 
the shock into the nerve before the lever begins 
to rise. This latent period is occupied by (a) 
passage of nervous impulse along nerve, (b) cer- 
tain changes taking place in the muscle itself 
before it begins to contract. The former varies 
according to length of nerve, the nerve-impulse 
travelling at the rate in the frog of about 28 
metres per second. The latter consists of some 
molecular changes in the muscle which occupy 
about xiofcli second. 

2. A period of contraction. 

3. A period of relaxation. 

Tetanus. — If single induction shocks follow 
one another slowly, a succession of curves are 
recorded on the drum. But if they are made 
to follow quickly, as when produced by the 
"magnetic interrupter," the muscle remains 
in a constant state of contraction known as 
tetanus. 

Change in Form.— When a muscle contracts, 
it shortens — that is, its ends come nearer to- 



46 MEMORANDA OF PHYSIOLOGY. 

gether, while the muscle itself becomes thicker; 
but there is no change of bulk : what it loses 
in length, it gains in thickness. 

Chemical Changes during Contraction. — 
(1) Muscle is normally neutral or faintly alka- 
line ; when it contracts it becomes acid, the 
acidity being due to the formation of sarco- 
lactic acid. (2) Carbonic acid is set free, not 
accompanied by a corresponding consumption 
of oxygen. Probably some complex body splits 
up, producing these two acids. (3) Oxygen is 
used up. Living muscle is constantly consum- 
ing oxygen, but more carbonic acid appears than 
can be accounted for by oxygen used. Other 
changes doubtless take place, of which little is 
known. 

Negative Variation of Muscle Current. — 
Whenever a muscle contracts, a change takes 
place in its electrical current. If a muscle when 
at rest, arranged so as to show its normal 
current, be made to contract or enter into a 
state of tetanus, the normal current will undergo 
diminution during the contraction. By refined 
me' hods it has been shown that the negative 
variation occurs during the u latent period" of 
stimulation. 

Production of Heat during Contraction. — 
Venous blood coming from an active muscle is 



MEMORANDA OF PHYSIOLOGY. 47 

warmer than blood from muscle in state of rest. 
The gastrocnemius of frog shows an increase of 
about one-tenth of a degree C. for each con- 
traction. The heat developed depends to some 
extent on the work done. 

Production of Sound during Contraction. — 
A sound is emitted from a muscle during con- 
traction. By placing the ear over a contracting 
muscle a deep-toned sound will be heard. 

Elasticity of Muscle. — Living muscle is 
elastic ; its elasticity is small, but very perfect. 
The muscle will elongate easily under the in- 
fluence of weights, and will return on their re- 
moval to its former length. 

Rigor Mortis. — Muscle on dying becomes 
rigid, but is again relaxed wheu putrefaction 
commences. Its tonicity has disappeared, so 
that on section it will not retract. It cannot 
readily be extended, and when extended does 
not return to its normal length. It has lost its 
translucent appearance, and become opaque ; 
its nerve-currents have disappeared. 

The chemical changes consist in the forma- 
tion of myosin, sar2olactic and carbonic acids. 
In the human corpse rigor mortis sets in from 
seven to twenty-four hours after death, and 
lasts from twenty-four hours to several days. 
As a rule, when it comes on slowly it lasts long. 



48 MEMOKANDA OF PHYSIOLOGY. 

It first affects the muscles of neck and jaw, then 
the trunk, upper extremities, and lower limbs. 
In exhaustion of muscular power prior to death, 
as in animals hunted to death, or soldiers killed 
late in an engagement, rigor mortis sets in very 
rapidly. 



Effects of Muscular Exercise. 

1. On the Lungs. — Elimination of Carbon. — 

The most important effect of muscular exercise 
is to increase the number of the respirations, and 
thereby the quantity of air passing in and out of 
the lungs, leading to an increased absorption of 
oxygen and elimination of carbonic acid. An 
adult, under ordinary circumstances, during in- 
spiration draws in 480 cu. in. per minute ; if he 
walk four miles an hour, he draws in five times 
as much, or 2,400 cu. in. ; if he walk six miles 
an hour, he draws in seven times as much, or 
3,260 cu. in. Probably the excessive absorption 
of O and formation of C0 2 takes place in the 
muscles. For effects of exercise on C0 2 given 
off during respiration, see p. 102. 

2. On the Circulation. — The increased work 
performed by the muscles requires increased 
activity on the part of the heart, to keep up 



MEMORANDA OF PHYSIOLOGY. 49 

the supply of arterial blood. The amount of in- 
crease is usually from 10-30 beats during exer- 
cise. After exercise, the heart's action becomes 
slower. Excessive exertion may lead to hyper- 
trophy of the left ventricle. 

3. On the Skin. — The minute arteries of the 
skin become dilated, the perspiration is in- 
creased, more water, salts, and acids pass off 
from the system. The amount of perspiration 
may be more than double the usual amount. 
The evaporation reduces the temperature of the 
body, which would tend to rise. There is dan- 
ger of a chill after the exertion is over, the skin 
still remaining wet while the heat of the body 
has declined. 

4* On the Voluntary Muscles. — The mus- 
cles grow and become firmer in substance. If, 
however, the exercise be excessive, after grow- 
ing to a certain extent, they will waste. 

5. On the Digestive System. — The appetite 
-increases with exerciee, especially for meat and 

fats j this is doubtless the result of the wear 
and tear of the muscles and the increased 
elimination of carbon. Digestion is more per- 
fectly performed, and the circulation through 
the liver and portal system quickened. 

6. On the Kidneys. — The water of the urine 
and the salts are probably lessened in conse- 

4 



50 MEMOEANDA OF PHYSIOLOGY. 

quence of the increased perspiration. It has been 
shown by various observers, including Parkes, 
that during active exercise the urea in the urine 
is not increased, but active exercise is followed 
by an increased appearance of urea. It appears 
therefore that to a certain extent muscular 
exercise increases the elimination of urea, the 
urea making its appearance in the period of rest 
succeeding the exercise. 

7. On the Temperature. — The temperature 
will not be increased ; the extra consumption 
of and the friction of the muscles tend to 
raise the temperature, but the evaporation from 
the surface of the skin will prevent much in- 
creased heat of body. 

SKIN 

Consists of — 

1. Epidermis or dermis. 

2. Dermis, corium, or cutis vera. 

3. Sweat-glands, nails, hairs, and sebaceous 
glands. 

1. The Epidermis forms a protective cover- 
ing over the surface of the body. It consists of 
a stratified layer of epithelial cells. The cells 
nearest the surface are flat and dry, those in 
the deepest layers are round and moist, while 
those occupying an intermediate position become 



MEMOKANDA OF PHYSIOLOGY. 51 

more and more flattened as they approach the 
surface. The term horny layer is given to the 
layer of cells nearest the surface, while the 
deep layer of round cells is called the rete mu~ 
cosum. Pigment, when present in the skin, is 
contained in the rete mucosum. The cells of 
the horny layer will not stain with carmine or 
logwood, but are colored by picric acid ; the 
cells of the deep layer are readily tinted by or- 
dinary staining fluids. The epidermis is evas- 
cular, contains no nerves, and is perforated by 
the ducts of the sweat glands. 

2. The Dermis, or true skin, is made up of 
an interlacing network of connective tissue, 
formed of white fibrous tissue, yellow elastic 
tissue, corpuscles, vessels, and nerves. In some 
parts of the body, as in the skin of the scrotum, 
perineum, penis, the cutis vera contains unstri- 
ated muscular fibres. There are also small mus- 
cular fibres in connection with the hair-follicles. 
Beneath the skin the subcutaneous tissues con- 
tain abundant adipose tissue. Numerous fine 
ridges are seen on the surface of the skin of the 
palm of the hand and sole of the foot. The 
ridges are caused by rows of little elevations of 
the cutis vera termed papilla. These little 
eminences are more or less conical, or some- 
times club-shaped ; they may be compound, 



52 MEMORANDA OF PHYSIOLOGY. 

and contain a capillary loop, nerve, and touch- 
corpuscle ; they project into the epidermis, and 
by raising it up as it were, form a ridge on the 
surface of the skin. They serve to increase the 
sensitiveness of the part, lodging a touch-cor- 
puscle in a favorable position for receiving sen- 
sations of touch. 

Sweat Glands are situated in the subcuta- 
neous tissue, and consist of a fine tube which 
forms the duct, its blind extremity being coiled 
up like a ball, and surrounded by a plexus of 
capillaries to form the gland. The duct is 
twisted like a corkscrew, and widens slightly at 
the orifice. The gland is lined by secreting 
epithelium. Each tube, if uncoiled, is said to 
measure J inch. 

Nails. — The nail consists of a root, body, and 
lunula. The root is that part of the nail which 
is covered by the skin, the body the external 
part, and the lunula is the whitish portion of 
the body near the root where the skin beneath 
is less vascular. 

Structure. — The nail closely resembles the 
epidermis, and is, in fact, a modification of that 
structure, consisting of hard and thin layers of 
cells on the surface, and round moist cells be- 
neath, corresponding to the rete mucosum. 

Posteriorly the nail fits into a groove which 



MEMORANDA OP PHYSIOLOGY. 53 

lodges its root. The part of the cutis vera to 
which the nail is attached is called the matrix, 
and is provided with large papillae. 

Hairs consist of a shaft and root. The shaft 
of the hair is cylindrical, and covered with a 
layer of imbricated scales, arranged with their 
edges upward. The substance of the hair con- 
sists of fibres, or elongated fusiform cells, in 
which nuclei may be discovered. There are 
also present in some hairs small air-spaces, or 
lacunas. In the coarser hair of the body there 
is a medulla, or pith, which is occupied by small 
angular cells and fine fat granules. The root of 
the hair swells out into a knob, and fits into a 
recess in the skin, called a hair follicle. 

The follicle consists of two coats, an outer, or 
dermic coat, continuous with the corium, and 
an inner, continuous with the epidermis, and 
called the root-sheath. The outer, or dermic 
coat, is formed of connective tissue, and is sup- 
plied by numerous vessels and nerves. It is 
separated from the root-sheath by a homogene- 
ous membrane. The inner, or epidermic coat, 
comes away when the hair is pulled out, and 
hence is called the root-sheath. It is made of 
two layers, the outer root-sheath and inner root- 
sheath. The outer root-sheath corresponds with 
the rete mucosum, and is thicker than the inner, 



54 MEMORANDA OF PHYSIOLOGY. 

and is composed of large round cells. The in- 
ner root-slieath corresponds with the horny layer. 
It is composed of flattened cells. The deeper 
cells of the inner root-sheath form what is called 
Huxley's layer. 

The bulbous root of the hair fits on to a pa- 
pilla, which is very large in the tactile nasal 
hairs of the cat. Small bundles of involuntary 
muscular fibres connect the corium with the 
root of the hair, so that in contracting they ele- 
vate the hair. 

The Sebaceous Glands consist of a small 
duct, which opens into the hair follicle, and is 
connected by its other end with a cluster of 
saccules lined with epithelium, which secrete 
fatty matters. 

The Perspiration is a clear acid colorless 
fluid with a peculiar odor. It contains nearly 
2 per cent, of solid matter. The amount must 
vary very considerably according to season, ex- 
ercise taken, or fluid ingested. On an average 
there is about thirty ounces lost by the skin in 
twenty-four hours, though under exceptional 
circumstances the same amount might be lost 
in an hour. The sweat is constantly being ex- 
haled from the body, either insensibly, or it 
collects in drops upon the skin, which gradually 
evaporate. The sweat consists of — 



MEMORANDA OF PHYSIOLOGY. 55 

1. Salts, 

2. Fatty acids, 

3. Fats, 

4. Nitrogenous bodies. 

The salts consist of sodium and potassium chlo- 
rides. The acids of acetic, butyric, formic, &c. 

The nitrogenous bodies include urea, am- 
monia, and other more complex bodies. It is un- 
certain how much urea is. excreted by the skin, 
if, indeed, any is, under normal circumstances. 

According to some, 100 grs. of nitrogenous 
material are thrown off by the skin daily. A 
certain quantity of C0 2 is given off by the skin, 
though probably small ; being - 4 V of that given 
off from the lungs. Babbits which have been 
covered with an impermeable varnish soon die. 
They become quickly cool, and have albuminu- 
ria. These effects are probably due to the ab- 
sorption or non-excretion of the sweat, and to 
rapid loss of heat from dilatation of the cutane- 
ous vessels. 

Absorption through the skin may take place 
under exceptional circumstances. Mercury, 
arsenic, and many other reagents are absorbed 
by the skin when rubbed on the surface. The 
skin will absorb iodine if exposed to steam im- 
pregnated with that reagent, the iodine being 
again excreted by the urine. 



Section 3- 

THE BLOOD. 

The blood, as it exists in the living body, is a 
red homogeneous alkaline fluid, of saltish taste 
and faint odor, and specific gravity 1052-1058. 
It consists of minute solid bodies, the corpus- 
cles, floating in a liquid — the liq. sanguinis. 

When drawn from the blood-vessels coagula- 
tion takes place, fibrin is formed, and a separa- 
tion takes place into clot and serum. 



f water 
s ,. - . . salts 

fLiq. sanguinis \ ftllmmen 

Blood in living J ] Sent" of fibrin 



body ) 



Corpuscles 



C water ) 

r t . . . I salts y serum 

n™* i ♦»* { Liq ' sangumiS 1 albumen J 

Coagulated j elements of fibrin 

blood ' I clot 

L Corpuscles f clot 



MEMORANDA OF PHYSIOLOGY. 



57 



If the blood, as it flows from the blood-ves- 
sels, be stirred with a stick, so as rapidly to 
cause coagulation, we have — 



Blood 



Liq. sanguinis 



I Corpuscles 



f elements of 
I fibrin 
•<! albumen 
1 salts 
[ water 



Fibrin 

I Defibrinated 
blood 



Red Corpuscles. — Human red corpuscles 
are circular biconcave discs of g-a V o m - m diam- 
eter. Examined singly with a power of 300 
they are of a yellowish color, and present a light 
transparent centre surrounded by an opaque 
rim or vice versa, according as the centre or 
edge is brought into focus. Examined edge- 
ways their biconcave shape will be readily seen. 
They probably have no nucleus and have no 
limiting membrane. The red corpuscles of 
mammals resemble those of man ; the elephant 
has the largest, 2 / 00 in. ; the musk deer the 
smallest, b ^ ou in. They are oval in the camel 
tribe. In birds, reptiles, amphibians, and 
fishes, the colored corpuscles are elliptical discs, 
the proteus having the largest, 4^ in. by T nu 
in. ; they have also a prominent central nucleus. 
The red corpuscles are soft in structure, elastic, 
and while pressure changes their shape, they 
readily regain it. When examined shortly after 



58 MEMORANDA OF PHYSIOLOGY. 

being drawn from the vessels, they are seen ad. 
hered together by their surfaces, and appear 
like rolls of coins. 

Effects of Reagents — Salt Solution. — When 
human blood is diluted with three-fourths per 
cent, salt solution, serum, or other saline solu- 
tion, the red corpuscles lose their sharp circular 
outline, minute prominences appear on the sur- 
face, and they assume an appearance termed 
" horsechestnut-shaped" from their resemblance 
to the prickly fruit of the horsechestnut. 

Carbonic Acid.— If the horsechestnut-shaped 
corpuscles be treated with carbonic acid gas, 
they again become smooth, though they do not 
regain their original biconcave form, but are 
more or less concavo-convex. 

Tannic Acid. — If the horsechestnut-shaped 
corpuscles are treated with two per cent, tannic 
acid, their haemoglobin separates itself from the 
stroma of the corpuscle, and is extruded in 
drop-like masses. 

• Boracic Acid. — In newt's blood, treated with 
two per cent, boracic acid, the nucleus becomes 
of deeper color at the expense of the disc, and 
a fine network of fibrils is displayed, which per- 
vades both disc and nucleus. This fine net- 
work is occupied normally by haemoglobin and 
a homogeneous interstitial substance. 



MEMORANDA OF PHYSIOLOGY, 59 

Water makes the corpuscles swell up and 
lose their haemoglobin, their outline becoming- 
very faint. 

[Heat. — When the living blood-cells of man 
and the mammalia are exposed to a tempera- 
ture of 52° C, 125| ° F. on the stage of the mi- 
croscope, globules form on the surface of the 
cell, which either separate at once or remain 
connected for a time by means of a slender 
pedicle. This is the frambcesiac appearance.] 

The red corpuscles contain — 

1. Haemoglobin, 

2. Globulin, 

3. Salts, 

4. Gases, 

5. Water. 

Haemoglobin contains C.H.O.N.S.Fe., and 

forms ninety per cent, of (dried) red corpuscles* 
It is soluble in water and serum, crystallizing 
in man and many mammals in elongated rhom- 
bic prisms, octahedral in the guinea-pig, and 
hexagonal in the squirrel. It can be obtained 
in crystals from the guinea-pig, rat, or mouse, 
but with difficulty from the blood of sheep, ox, 
or pig. 

Preparation. — The haemoglobin is made to 
leave the corpuscles by shaking with ether or 



I 



60 MEMORANDA OF PHYSIOLOGY. 

by alternately freezing and thawing the blood. 
The blood is thus rendered translucent or 
4 ' laky ; " one quarter of its bulk of alcohol is 
added, and it is placed in a temperature of 0° C. 
to crystallize. 

Haemoglobin exists in the human blood in 
two forms, one in loose combination with oxy- 
gen — oxy-haemoglobin — and the other as re- 
duced haemoglobin. If oxy-haemoglobin be 
acted upon in solution with a reducing agent, 
as an alkaline solution of ferrous sulphate and 
tartaric acid, it is reduced and becomes of a 
purplish red color. Oxy-haemoglobin gives in 
the spectrum two narrow dark bands in the 
green, reduced haemoglobin a single broad dark 
band intermediate in position between the two. 
Haemoglobin readily decomposes, forming hae- 
matin and globulin. Haematin forms with HC1 
a compound called haemin, which crystallizes in 
minute rhombic prisms. Haemoglobin gives a 
characteristic blue color when treated with tr. 
guaiaci and solution of peroxide of hydrogen. 

2. Globulin or Paraglobulin. See Coagu- 
lation. 

3. Salts.— These amount to one per cent, of 
the dried solids, the principal salts being those 
of potassium and phosphates. 

4. Gases. — Oxygen loosely combined with 



MEMORANDA OF PHYSIOLOGY. 61 

the haemoglobin. Nitrogen in small quantity. 
The existence of carbonic acid gas in the cor- 
puscles is uncertain; by far the greater part 
exists in the serum. 

5. Water forms 56.5 per cent, of the corpuscles. 

Origin of Red Corpuscles. — In the embryo — 

1. From cells in the vascular area of mesoblast, 

2. By division. 3. From white corpuscles. 
Adult. — From white corpuscles, transitional 
forms exist in medulla of bone and spleen. 

Fate of Red Corpuscles. — Probably broken 
up in spleen. Haemoglobin probably forms bile- 
pigments. 

White Cokpuscles ok Leucocytes.— The 
white corpuscles in human blood are sphe- 
roidal, finely granular masses of rgVu i n ch in di- 
ameter. Some of them are less, being smaller 
than the red corpuscles. They have no cell- 
wall, and their substance consists of protoplasm. 
According to Heitzmann, their granular appear- 
ance is due to a fine intercellular network, having 
small dots at the intersections of the network. 
In the meshes of the network is a hyaline sub- 
stance. They possess one or two nuclei, which 
are readily brought out by acetic acid. Yv r hen 
examined in a fresh state, especially if placed 
on a warm stage, they exhibit spontaneous 
change of shape like the amoebae, these move- 



62 MEMORANDA OF PHYSIOLOGY. 

merits being termed amoeboid. The movements 
consist in a protrusion of processes of proto- 
plasm, which are retracted and other processes 
protruded. 

Both in human and newt's blood there are 
some colorless corpuscles which contain coarser 
granules than others ; these are called granular 
corpuscles. The white corpuscles will take up 
colored foreign particles, as vermilion. They 
are found in various tissues of the body, as in 
the meshes of the retiform tissue of lymphatic 
glands, tonsils, solitary glands, etc. In* inflam- 
mation they pass through the walls of the capil- 
laries into the tissues. They are present in the 
blood in the proportion of 1 per 300 red corpus- 
cles after a meal, and 1 per 800 during fasting ; 
they are much more numerous in some diseases, 
as in leucocythasmia. 

Composition : 

1. Several albuminous substances. 

2. Lecithin and glycogen. 

3. Salts, mainly potassium and phosphates. 

4. Water. 

Origin. — Probably from the lymphoid tissues 
of the body, i.e., lymphatic glands, solitary 
glands, spleen, etc., by division of the leu- 
cocytes existing there. The thoracic duct and 
lymphatics are constantly pouring white cells 



MEMORANDA OF PHYSIOLOGY. 63 

into the blood, derived from the mesenteric and 
other lymphatic glands. 

Fate. — They are converted into red corpus- 
cles. During inflammation they pass through 
the capillary walls, and become pus-cells ; it is 
also probable they are utilized in other ways 
than in forming pus, possibly being converted 
into the cell- elements of new tissues, or taking 
the place of worn-out cells throughout the body. 

Liq. sanguinis is a clear yellow alkaline 
fluid in which the corpuscles float. It may be 
obtained by allowing the slowly coagulable 
blood of the horse to stand in a tall vessel sur- 
rounded by ice. The temperature of 0° C. pre- 
vents coagulation, the corpuscles subside, and 
the clear fluid may be removed by pipette. Its 
composition may be described as serum plus the 
elements of fibrin. 

Serum. — When blood has coagulated, and the 
clot separated, a thin yellow transparent alka- 
line fluid is left of specific gravity 1028. 

It consists of — 

1. Albumen. 

2. Paraglobulin. 

3. Extractives. 

4. Fatty matters. 

5. Salts. 

6. Water and gases. 



64 MEMORANDA OF PHYSIOLOGY. 

1. Albumen exists in combination with tire 
sodium as an albuminate. It is in the form of 
serum-albumen, differing from egg-albumen in 
not being coagulated by ether. On boiling the 
serum, the albumen coagulates ; the fluid, after 
being deprived of its albumen, is called serosity. 

2. Paraglobulinj one of the fibrin-factors, is 
present, all the fibrinogen disappearing during 
coagulation. 

3. Extractives include kreatin, kreatinin, 
urea, uric acid, and traces of grape-sugar. 

4. Patty Matters in minute division, and 
combined with sodium as soaps. * 

5. Salts 3 principally sodium salts, in combina- 
tion with 01. and C0 2 , smaller quantities of po- 
tassium and calcium phosphates and sulphates. 

6. Gases, — C0 2 , partly free, and partly in 
combination with the sodium. 

GASES OF THE BLOOD. 

In 100 vols, of 

Carbonic 
Oxygen. acid. Nitrogen. 

Arterial blood there are 20 vols. 39 vols. 1 or 2 vols. 
Venous blood there are 12 vols. 46 vols. 1 or 2 vols. 

measured at 760 mm. and 0° C. 

Oxygen. — The greater part of the oxygen of 
the blood is in loose chemical composition with 
the haemoglobin, only a small part is simply dis- 



MEMORANDA OF PHYSIOLOGY. 



65 



solved. If water in which oxygen is simply dis- 
solved be subjected to diminished pressure in a 
mercurial air-pump, the gas begins to be given 
off immediately the pressure is reduced, and the 
amount disengaged is proportional to the pres- 
sure ; in other words, it is said to follow Dal- 
ton's law. But if arterial blood be submitted in 
like manner to diminished pressure, no oxygen 
will be given off till the pressure sinks to one- 
sixth of an atmosphere (125 mm.). The gas is 
then rapidly given off, and the blood becomes 
dark. 

Carbonic Acid. — The gas does not combine 
with haemoglobin, but is present in the blood 
(a) dissolved in the serum, (b) major part in 
combination with sodic carbonate, forming a 
hydro-sodic carbonate. Volume for volume se- 
rum yields as much carbonic acid as blood. 

Nitrogen. — This gas is simply dissolved in 
the serum. 



COAGULATION OF THE BLOOD. 

Blood drawn from a living animal into a 
beaker first becomes viscid and then is converted 
into a jelly. This jelly is the same bulk as the 
previous blood. Finally, the jelly contracts, 
forming the clot, and a yellow clear liquid, the 
serum, oozes out. In man blood becomes viscid 
5 



66 MEMORANDA OF PHYSIOLOGY. 

in two or three minutes, forms a jelly in five or 
six minutes later, and a few minutes later still 
the serum begins to appear. In the horse coag- 
ulation goes on more slowly, so that the corpus- 
cles have time to sink before the jelly stage is 
reached ; so that a yellowish stratum is formed 
on the top, free from red corpuscles, but con- 
taining white; called the "buffycoat." This 
buffy coat appears in human blood in certain 
inflammatory conditions. 

Many circumstances favor or postpone the 
coagulation of the blood. The principal are 

Circumstances favoring Coagulation. 

1. Contact with foreign matter. 

2. Moderate temperature, 100° to 120° F. 

3. Stasis of blood in the vessels, or injury to 
the lining membrane. 

Circumstances retarding Coagulation. 

1 . Contact with lining membrane of the blood- 
vessels. 

2. Cold 0° C. indefinitely postpones. 

3. Addition of neutral salts, or the caustic 
alkalies. 

The immediate cause of coagulation is the 
formation of fibrin, of which blood yields about 
. 2 per cent. Fibrin is formed by the union of 



MEMORANDA OF PHYSIOLOGY. 



67 



two albuminous bodies present in the blood — 
paraglobulin and fibrinogen. A third body, 
supposed to be of the nature of a ferment, is 
essential, or at any rate favors the process. 

Fibrin. — This substance may be obtained by 
stirring some freshly drawn blood with a stick 
or bundle of twigs. It is a white stringy body, 
insoluble in water or alcohol, soluble in alkalies, 
lactic, phosphoric, and acetic acids. H. CI con- 
verts it into syntonin. 

Paraglobulin may be obtained from serum 
or diluted liq. sanguinis, by passing through it 
a stream of C0 2 or saturating it with Nad. It 
is thrown down as a granular white precipitate. 

Fibrinogen may be obtained in a similar 
manner by passing C0 2 through hydrocele or 
pericardial fluid, or saturating with NaCl. 

The Ferment is obtained by adding defibrin- 
ated blood to twenty times its bulk of alcohol; 
a precipitate of albuminous bodies with the fer- 
ment is thrown down. Distilled water dissolves 
out the latter, and if added to a solution con- 
taining fibrinogen and paraglobulin, coagulation 
quickly ensues. 

Contact with foreign matter quickly deter- 
mines coagulation, while contact with the 
endothelium of the blood-vessels exercises a 
restraining influence. If the jugular vein of a 



68 MEMORANDA OF PHYSIOLOGY. 

horse be ligatured at both ends and cut out, the 
blood will remain fluid for one or two days, but 
will clot on being withdrawn. Blood will re- 
main fluid for several days in the excised heart 
of the turtle. Horse's blood allowed to stand 
surrounded by ice will remain fluid indefinitely. 
Blood drawn into a saturated solution of sodic 
phosphate will remain fluid, but will clot if di- 
luted. The share taken by the corpuscles in 
coagulation is uncertain. Fluids containing 
white corpuscles clot more firmly and quickly 
than those containing red only. 

Amount of Blood in Body. — Probably about 
T^-th of the body-weight as estimated by the 
hemoglobin of the blood. 



Qtttxon h. 

THE CIRCULATION 

The circulation is carried on by means of the — 
1. Heart, beating about seventy-five times 
per minute, alternately receiving blood from the 
venous system, and discharging it into the pul- 
monary artery and aorta. 



forming channels through which the blood is 
carried to the system, assisting the heart in 
maintaining the circulation, and regulating the 
supply of blood to different parts. 

3. Capillaries. — Canals of minute calibre, 
with thin permeable elastic walls, allowing both 
liq. sanguinis and white corpuscles to pass 
through their walls into the surrounding tissues. 

4. Veins, forming channels batik to the heart, 
provided with muscular walls and valves, and 
being sufficiently capacious to hold the total 
blood of the body. 



70 MEMORANDA OF PHYSIOLOGY. 

THE HEART. 

The heart consists of four chambers with con- 
tractile walls, situated in the chest, and sur- 
rounded by a fibro-serous sac — the pericardium 
in which it works. 

The Pericardium. — This membranous sac is 
attached below to the diaphragm, while its upper 
and narrower part surrounds and is attached to 
the great vessels connected with the base of the 
heart. It consists of an external fibrous layer, 
and an internal serous sac. The fibrous layer is 
a tough dense membrane, attached below to the 
central tendon and muscular fibres of the dia- 
phragm ; above it is attached to the great ves- 
sels, and is continuous with their external coats. 
The serous covering consists of a parietal layer, 
which is united to the inner surface of the 
fib.rous layer, and a visceral which is reflected 
round the great vessels enclosing the aorta and 
pulmonary artery in a common sheath. In 
structure the serous layer resembles other ser- 
ous membranes. 

General Description of the Heart. — In form, 
the heart resembles a cone, its base being directed 
upward, backward, and to the right, its apex 
downward, forward, and to the left. In part 
it is covered by the lungs, especially during in- 



MEMORANDA OF PHYSIOLOGY. 71 

spiration. Its apex beat is felt at the fifth inter- 
costal space, two inches below the nipple, and 
one to the inner side of left nipple line. In order 
to map the outline of the heart on the chest- 
wall, define the base by drawing a transverse line 
across the sternum corresponding with the upper 
border of the third costal cartilages, continuing 
it i in. to right of sternum, and 1 in. to left. 
Lower border. — Draw a line from the apex-beat 
through the sterno- xiphoid articulation to the 
right edge of the sternum. Bight border. — Con- 
tinue the last line with an outward curve to join 
the right end of the base line. Left border. — 
Draw a line curving to the left (inside the nip- 
ple) from the apex- beat to the left end of the 
base line. (Holden.) 

Cavities of Heart. — The keart contains four 
chambers, two auricles and two ventricles. 

The Right Auricle receives the blood from 
the superior and inferior vense cavas at its upper 
and lower posterior angles. The septum between 
the two auricles forms the posterior wall, and 
presents the fossa ovalis (the remains of the fora- 
men ovale), which is surrounded by a border (ex- 
cept below), the annuhis ovalis. Between the 
two orifices of the venas cavse is the tubercle of 
Lower, and in front of the opening of the infe- 
rior vena cava is the Eustachian valve. The coro- 



72 MEMORANDA OF PHYSIOLOGY. 

nary vein opens into the auricle between the 
inferior cava and auriculo-ventriculo- opening, 
and is guarded by the valve of Thebesius. The 
auricular appendix is a tongue-shaped append- 
age, which projects from the anterior angle, and 
covers the root of the aorta. The cavity of the 
auricle is smooth, except that of the auricular 
appendix, which presents the muscular bands 
called musculi pectinati. The openings into the 
right auricle are the following : — 1, openings of 
vense cavae ; 2, auriculo-ventricular opening ; 3, 
orifice of coronary sinus ; 4, openings of one or 
two small veins of right ventricle ; 5, foramina 
Thebesii, which are small depressions, some of 
them transmitting minute veins. 

The Right Ventricle forms the right border 
and chief part of interior surface of heart. At 
its base are two orifices guarded by valves, the 
auriculo-ventricular and the pulmonary artery. 
The inner surface presents muscular elevations 
termed columns carnea, some of which are at- 
tached by their extremities to the wall of the 
ventricle, others in their whole length, while a 
third set are connected by their bases to the 
ventricular wall, and are connected by their 
other extremities to the segments of the tricus- 
pid valves, by means of the chordm tending. 

The Left Auricle is situated at the posterior 



MEMORANDA OF PHYSIOLOGY. 73 

part of the base of the heart. It receives two 
pulmonary veins on each side, and opens into the 
left auricle through the mitral valve. The in- 
terior of the left auricle is smooth like the right, 
its appendix presenting musculi pectinati. 

The Left Ventricle forms the left margin of 
the heart, the greater part of the posterior, and 
a small part of the anterior surface. Its walls 
are some three times as thick as the right ven- 
tricle, its musculi papillares are larger, and the 
chordas stronger. Like the right ventricle, it 
has two orifices, auHculo-ventricular , guarded by 
the mitral, and the aortic, guarded by the semi- 
lunar mkes. 

Endocardium. — The internal membrane lin- 
ing the heart closely resembles the lining mem- 
brane of the arteries. It consists of a single 
layer of tessellated epithelium, with a connec- 
tive-tissue layer beneath. 

Valves of Heart. — The mitral and tricuspid 
valves are situated at the auriculo-ventricular 
orifices, and prevent the passage of blood into 
the auricle during the ventricular systole. They 
consist of flaps or cusps, two in the mitral, and 
three in the tricuspid, connected by their bases 
to the auriculo-ventricular orifices ; their free 
margins and lower surfaces give attachment to 
the chordaa tendinse which connect them with 






74 MEMORAm>A OF PHYSIOLOGY. 

the musculi papillares. They are formed of a 
duplicature of the lining membrane of the 
heart, strengthened by connective tissue. Dur- 
ing- the ventricular systole, the pressure of the 
blood in the ventricles presses their free edges, 
or marginal surfaces together, the musculi pa- 
pillares regulating the tension of the chords and 
preventing the valves from becoming retroverted 
into the auricles. 

The semilunar valves guard the aortic and 
pulmonary openings. They consist of three 
semicircular folds attached by their convex 
margin to the wall of the artery at its junction 
with the ventricle, and are formed of a redupli- 
cation of the lining membrane strengthened by 
fibrous tissue. In the centre of each free mar- 
gin is a little nodule, the corpus Arantii, the 
three meeting in the centre when the valves are 
closed. On each side of the corpora Arantii is 
a thin semilunar marginal surface, where the 
fibrous tissue is absent, called the lunula, these 
surfaces come in contact when the valves close. 
After the systole of the ventricles, the tension 
of blood in the aorta and pulmonary artery 
close the valves by distending them and press- 
ing the marginal surfaces together. The semi- 
lunar valves during the ventricular systole are 
pressed back against the walls of the aorta, and 



MEMORANDA OF PHYSIOLOGY. 75 

hence, according to Briicke, prevent the filling 
of the coronary arteries which arise from the 
sinus of Valsalva during the ventricular systole, 
the coronary arteries being rilled after the 
closure of the valves and during the diastole of 
the ventricle. 

Sounds of the Heart. — First sound. — Best 
heard at the apex-beat. It is synchronous with 
the ventricular systole, commencing immediately 
the ventricle begins to contract, but ceases be- 
fore its completion. It is louder, longer, duller, 
than the second sound. Various explanations 
have been given as to its cause, none of them 
are entirely satisfactory. 

1. Closure of auriculo- ventricular valves. 

2. Muscular sound of contraction of ventricles. 

3. Cardiac impulse against chest-wall. 
The second sound is short and sharp, is heard 

best at junction of third costal cartilage with 
sternum, and corresponds to the closure of the 
semilunar valves. Between the first and second 
sounds the pause is very short, but between the 
second and succeeding first the pause is longer, 
and is about equal in duration to the time oc- 
cupied by the first and second sounds together. 
The sounds have been likened to the pronuncia- 
tion of the syllables lubb, diip. 
A Cardiac Revolution. — A complete cardiac 



76 MEMORANDA OF PHYSIOLOGY. 

cycle includes the entrance of blood into the 
auricles, the systole of the latter filling the ven- 
tricles, and the ventricular systole propelling 
the blood into the pulmonary artery and aorta. 
During the pause after the contraction of the 
ventricles, the vena3 cavse and pulmonary veins 
are pouring blood into the auricles. The au- 
ricular systole commences in the muscular fibres 
surrounding the great veins, the contraction 
running through vessels and auricles in a peri- 
staltic wave, emptying the contents of the ves- 
sels into the auricle, and then emptying the 
auricle itself, the appendix being the last part to 
contract, the ventricles becoming filled. Re- 
gurgitation into the great veins is hindered by — 

1. Peristaltic contraction of muscular walls 
of veins. 

2. Aspirating power of thorax during in- 
spiration. 

3. Valves at junction of subclavian and in- 
ternal jugular veins. 

Regurgitation into the coronary sinus is pre- 
vented by valve of Thebesius. Then follows 
immediately the ventricular systole; the ven- 
tricles become tense and hard, shorter and 
thicker ; the heart twisting on its long axis 
strikes the chest- wall, and ejects the contents of 
the ventricles (about 5 oz. ) into the pulmonary 



MEMORANDA OF PHYSIOLOGY. 77 

artery and aorta. At the commencement of the 
v. systole the auriculo-ventricular valves close, 
and the semilunar open ; and at the termination 
of the systole the semilunar close and auriculo- 
ventricular open. The time occupied by a com- 
plete beat is slightly over a second. It will be 
divided in the following manner : 

Contraction of auricles = £ sec. 

Dilatation of auricles = f sec. 
Contraction of ventricles = % sec. 

Dilatation of ventricles = f sec. 
or, 

Auricular systole = i sec. 

Ventricular systole = f sec. 

Pause = | sec. 

Endocardial Pressure. — Goltz and Gaule 
found the maximum pressure in the left ventri- 
cle of a dog amount to 140 mm. of mercury, 60 
mm. in the right ventricle, and 20 mm. in right 
auricle. Immediately after the systole a nega- 
tive pressure of — 52 to — 20 mm. was observed 
in the left ventricle, in the right ventricle about 
— 17 mm., and in the right auricle — 12 to — 7 
mm. While to some extent this negative pres- 
sure is due to the aspirating power of the 
thorax during inspiration ; yet, as a considera- 
ble negative pressure is observed after the chest 



78 HEMOBANDA OF PHYSIOLOGY. 

is opened, it would appear that the suction- 
power or active dilatation of the ventricles, and 
in a lesser degree the auricles, is of consider- 
able service in carrying on the venous circula- 
tion. 

THE ARTERIES. 
Structure. — The arteries have three coats — 

C Epithelial. 
1. Internal •< Sub -epithelial. 
( Elastic. 

* Middle j «- 

3. External — Connective tissue. 

1. Internal. — This coat may be readily 
stripped off the inner surface of the artery as a 
transparent, colorless, elastic, and brittle mem- 
brane. It is formed of — 

(a) An epithelial layer, consisting of a single 
layer of thin, elongated cells, with nuclei. 

(b) Sub- epithelial layer, composed of branch- 
ing corpuscles lying in cell-spaces of homogene- 
ous connective tissue. 

(c) Elastic layer, consisting of a fine mem- 
brane marked with interlacing network of fibres 
and perforated with round openings, and termed 
fenestrated membrane of Henle. 

2. Middle or Muscular. — In the small and 
medium-sized arteries the middle coat consists 



MEMOKANDA OP PHYSIOLOGY. 79 

of pure non-striated muscular fibre, arranged 
transversely round the artery with only a slight 
admixture of elastic tissue. In the larger arte- 
ries yellow elastic fibre predominates, and. in- 
deed, the aorta consists of nearly pure yellow 
elastic tissue. 

3. External coat, or tunica adventitia, con- 
sists of fine connective tissue. 

Circulation in the Arteries. — At each ven- 
tricular systole some five ounces of blood are 
forced into an already overfilled aorta and arte- 
rial system ; the effect of this being (1) to increase 
the tension in the arterial system and distend 
the elastic walls of the aorta and large arteries, 
(2) to send a wave impulse along the blood in 
the arteries, which is gradually lost before reach- 
ing the capillaries and which can be felt in the 
radial and other arteries as the pulse. If the 
arteries were rigid tubes, the intermittent action 
of the heart would cause an intermittent flew 
of blood from the arteries to the capillaries. 
The effect of the ventricular systole is to dis- 
tend the walls of the aorta, to store up force 
during the systole to be utilized in continuing 
the circulation during diastole, the recoil of the 
elastic walls assisting to convert the intermit- 
tent blood-stream into a continuous one. If a 
large vessel, as the carotid, is divided, an inter- 



80 MEMORANDA OF PHYSIOLOGY. 

mitten t stream of blood flows out, but a wound 
of a very small artery yields a steady stream. 

Arterial Pressure. — The pressure of blood in 
the arteries is measured by connecting the caro- 
tid artery of rabbit or dog with a U -shaped 
tube containing mercury. If a float on the mer- 
cury be made to carry a small camel's-hair brush 
or pen, the oscillations of the mercury caused 
by the varying tension in the blood-vessels can 
be recorded by the brush or pen writing on a 
revolving surface. Such an arrangement is 
called a kymograph. The pressure in the arte- 
ries undergoes variations which correspond (1) 
with each systole of the left ventricle, (2) with 
the movements of respiration. The average 
pressure of the blood in the large arteries is 
greater than in the small. 

The pressure in the carotid of man probably 
amounts to about 150-200 mm. (6-8 in.), in the 
aorta 250 mm. (9.8 in.), and in the brachial 
110-120 mm. (4.3-4.7 in.) of mercury. 

Velocity of the Flow.— The rate of move- 
ment of the blood in the arteries has been 
measured principally in the carotids of the 
horse, dog, and rabbit. In the horse Volkmann 
found the velocity to be 300 mm. per second in 
the carotid, 165 mm. in the mamillary, and 56 
mm. in the metatarsal. Various instruments are 



MEMORANDA OF PHYSIOLOGY. 81 

employed for this purpose, the Stromvliv of 
Ludwig and the H<xm.atochometer of Vierordt 
being the principal. In order to measure the 
time occupied by the circulation of any portion 
of blood, ferrocyanide of potassium is injected 
into the jugular vein, and the blood from the 
peripheral end of the same vein tested from 
time to time. In this way a complete circula- 
tion has been found to take place in 15 seconds 
in the dog, and 23 seconds in the human sub- 
ject {Hermann). 

The Pulse. — The impulse or shock caused by 
the overfilling of the aorta during the ventricu- 
lar systole is the cause of the pulse. This pulse- 
wave travels at the rate of 9-10 metres (28-30 ft.) 
per second along the arteries, and is lost at the 
capillaries. This pulse-wave must be carefully 
distinguished from the blood-current, the latter 
travelling only some 300 mm. (12 in.) per sec- 
ond ; the former stands in the same relation to 
the moving blood as does a wave on the surface 
to the current of a slowly flowing river. The 
duration of "the ventricular systole being f 
second before the end of the systole, the pulse - 
wave would have travelled about 12 ft., if that 
were possible, so that the beginning of each 
wave is lost al^ the periphery before the end of 
it has left the ventricle. The more rigid the 
6 



82 MEMORANDA OF PHYSIOLOGY. 

arteries the faster the wave travels ; the more 
distensible the more slowly it travels. If the 
finger be applied to the radial artery, the artery 
will be felt to expand beneath the finger some 
75 times a minute ; under some circumstances 
the pulse-wave will feel to be double or dicrotic. 
This dicrotism is shown by the sphygmograph 
to be constant in health, but is more marked 
when the tension in the arteries is low, and the 
arterial walls more distensible than usual, as in 
febrile conditions of the system. In a sphygmo- 
graphic tracing, the primary wave is due to the 
shock given to the blood in the arteries by the 
systole of the ventricles ; the dicrotic wave is 
probably in part due to the closure of the aortic 
valves, in part it is a wave of oscillation ; the 
predicrotic wave is also a wave of oscillation. 
Waves of oscillation are seen when fluid is in- 
jected into an elastic tube (as in an artificial 
scheme of the circulatory apparatus), following 
the primary wave, and are due to the inertia of 
the elastic walls and contained fluid. 

The Contractility which the arteries possess, 
in virtue of the muscular fibres in their walls, 
fulfils several useful purposes. 

1. It assists in arresting hemorrhage when 
an artery is completely divided. 



MEMORANDA OF PHYSIOLOGY. 83 

2. Under the influence of the vaso-motor sys- 
tem it regulates the supply of blood to a part. 

3. It enables the whole vascular system to 
accommodate itself to the amount of blood in 
the body. 

Frequency of Pulse. — The frequency of the 
pulse depends upon many various conditions. 
The emotions, amount of exercise, state of the 
digestion, inflammations, fevers, all exert an in- 
fluence on the pulse rate, through the medullary 
centres which regulate the contractions of the 
heart and muscular fibres of the arteries. 
Other influences may be classified under — 

Temperature. — Heat increases, cold slows. 

Position of body. — In a sitting position it is 
faster than in a horizontal position, and in 
standing up it is faster than when sitting down. 

Age.— In the foetus it is 150-200. In the 
adult about 75 ; it increases in old age. 

Sex. — It is faster in females than males. 

THE CAPILLARIES. 

Structure of Capillaries. — The smaller arte- 
ries end in a fine network of vessels, which dif- 
fer in structure from the arteries and veins, 
their walls containing no muscular elements, 



84 MEMORANDA OF PHYSIOLOGY. 

but consist of a delicate, transparent wall. 
Their walls consist of a single layer of elongated ' 
epithelium, continuous with that of the arteries ; 
the epithelium is rendered apparent by injection 
of solution of silver nitrate and exposing to 
light, the reagent darkening the intercellular 
material and rendering the outline of the cell 
apparent. Their nuclei can be stained with 
logwood. In the vessels slightly larger than 
the capillaries a layer of elongated muscular 
fibre cells is added. 

Size. — Their average size in the human body 
is about ainToth of an inch, but they differ in 
different parts of the body. They are compar- 
atively large in the marrow of bone ; large also 
in skin, small in lung, muscle, and brain. The 
network is close in lung and muscle. 

Circulation in Capillaries. — The velocity of 
the blood in the capillaries is very much less 
than in arteries or veins, being about .57 mm. 
to .75 mm. per second (1.4 — 1.8 inch per 
minute). But a very small portion of the capil- 
lary system is traversed by any one blood-cor- 
puscle. The flow is constant, not intermittent, 
as in the larger arteries. The red blood-cor- 
puscles for the most part travel in the mid- 
stream, the white .corpuscles moving more 
slowly along the side. The thin capillary walls 



MEMOKANDA OP PHYSIOLOGY. 85 

allow the liq. sanguinis readily to pass through, 
and so bring the blood in direct contact with 
the tissues, and also nourish parts by irrigation 
in which there are no capillaries, as cartilage 
and the cornea. Under certain circumstances, 
as in inflammation, the white corpuscles push 
through the capillary wall into the tissues ; 
probably this emigration to a smaller extent 
goes on as a natural process. The movement of 
blood in the capillaries is dependent upon the 
action of the heart, modified by the arteries. 
This constitutes the vis a tergo. Some main- 
tain that there is also another motor force called 
the capillary force. It is asserted that in the 
lower classes of animals and in plants there is 
some power independent of a vis a tergo, by 
which the nutritive fluid moves through the 
vessels. Cases have occurred in which the heart 
has been absent in a foetus during intra-uterine 
life, and yet the circulation must have been 
maintained. It is supposed that the ' ' capillary 
power " supplies the place of a heart up to the 
period of birth in the acardiac foetus. It is 
asserted by Draper that the tissues have an 
affinity for arterial and a repulsion for venous 
blood, the opposite holding good in the lungs. 
The vis a tergo derived from the heart is, how- 
ever, capable of maintaining the circulation in 



86 MEMORANDA OF PHYSIOLOGY. 

the capillaries, and it is doubtful if any other 
force, in the higher animals at least, exists. 

\ 

THE VEINS. 

Distribution.— The veins carry the blood 
from the capillaries to the heart. They ramify 
through the body like the arteries, but they are 
more numerous, anastomose more freely, and 
are of greater capacity* They usually accom- 
pany the arteries ; but there are exceptions, as 
the hepatic, sinuses of the skull, and veins of 
spinal cord. 

Structure. — The veins have thinner walls 
than the arteries. They have the following 
coats : 

1. Internal. — This coat closely resembles the 
inner coat of the arteries. 

2. Middle. — This coat is thinner and less mus- 
cular, and contains more white fibrous tissue 
than the middle coat of arteries. The muscular- 
ity of the middle coat is best marked in the 
splenic and portal, and least marked in the 
hepatic part of the inferior vena cava and sub- 
clavian veins. 

3. External. — This coat consists of connec- 
tive tissue and elastic fibres. In certain veins 
this coat contains a considerable quantity of 



MEMORANDA OF PHYSIOLOGY. 87 

muscular tissue, as in the abdominal cava, iliac 
and renal. The striated muscular fibre of the 
heart is prolonged for some distance on the walls 
of the pulmonary veins and venae cavae. Mus- 
cular tissue is wanting in most of the veins of 
the brain and pia mater, retina, venous sinuses 
of dura mater, cancellous veins of bone. 

Valves. — The valves consist of semilunar 
folds of lining membrane strengthened by in- 
cluding connective tissue. They consist for the 
most part of two flaps or pockets, which come in 
contact by their free margins, and prevent re- 
flux of blood toward the capillaries. The veins 
of the extremities, neck, and scalp have numer- 
ous valves, while they are absent for the most 
part in the deep veins of the abdomen, chest, 
and cranium. Many other veins are destitute 
of valves. Such are the venae cavae, portal, 
hepatic, renal, uterine, pulmonary, and sinuses 
of skull. There are a few in the intercostal 
and azygos. 

The forces -which propel the blood in the 
veins are — 

1. Vis a tergo — heart's action. 

2. Vis a fronte — aspiration of the thorax. 

3. Muscular contraction. 

1. The vis a tergo or force exerted by the 
heart in assisting the flow of blood in the ven- 



88 



MEMORANDA OF PHYSIOLOGY. 



ous system is probably not great, the velocity of 
the blood in the small veins being small. 

2. The vis a f route or force supplied by the 
suction action of the chest during inspiration is 
much more considerable. When an ordinary in- 
spiration is taken, not only is air drawn into the 
air-passages by the expanding chest, but the 
blood in the great veins external to the chest is 
sucked toward the right auricle. This effect 
is more powerful if a deep inspiration is taken. 
During an ordinary expiration the sucking ac- 
tion becomes nil, while during a powerful expi- 
ration, as in blowing or coughing, the expiratory 
effort obstructs the flow of blood into the chest 
and causes congestion of the venous system. 

3. During muscular exercise the veins are 
compressed by the contracting muscles, the ef- 
fect being to drive the blood toward the heart, 
the valves preventing its return toward the 
capillaries. 

The velocity of the blood in the venous system 
is small when compared with the arteries, 
though greater in the large veins near the heart 
than in the smaller veins. It is about 200 mm. 
per second (7 to 8 inches) in the jugular vein 
of dog. The pressure in the crural vein of the 
sheep has been shown to be 11.4 mm. of mer- 
cury (.4 inches), while in the subclavian it was 



MEMORANDA OF PHYSIOLOGY. 



89 



—1 mm. to —5 mm. daring inspiration, the 
mean pressure being —.1 mm. 



INNERVATION OF THE HEART AND AR- 
TERIES. 

The nervous mechanism of the heart and ar- 
teries consists of — 

1. Heart. 

1. Intrinsic cardiac ganglia. 

2. Centres in the medulla — (a) inhibitory cen- 
tre, (b) accelerating centre. 

3. Inhibitory nerves, i.e., vagi. 

4. Accelerating nerves, i.e., sympathetic. 

2. Arteries. 

1. Vaso-motor centres — medulla, cord, gan- 
glia. 

2. Vaso-motor nerves, i.e., (a) vaso- constric- 
tor, (b) vaso-dilator. 

I. 1. Intrinsic Ganglia— Automatic Action, 
— If a frog's heart be removed from the body 
and emptied of blood, it will continue to beat 
for hours, or even days. It is therefore clear 
that its action is automatic, and not dependent 
on any external influence. If the heart is bi- 
sected longitudinally, each half will go on beat- 
ing. If the auricles are separated from the 



90 MEMOKANDA OF PHYSIOLOGY. 

ventricles, both auricles and ventricles will pul- 
sate ; but if divided below the auriculo-ventric- 
ular groove, the part with the auricles at- 
tached will continue to beat, the ventricular 
part being motionless. It will be found that 
the parts which continue to beat contain gan- 
glia. The ganglia are present in the walls of 
the sinus venosus (Remak's ganglia), auricular 
septum, auriculo- ventricular groove (Bidder's 
ganglia). 

2. Extracardiac Centres. — The inhibitory 
centre is situated in the medulla, and is con- 
stantly in action. It is capable of being influ- 
enced by the excitation of various sensory 
nerves. The accelerating centre is also in the 
medulla ; it is not constantly in action. These 
centres are largely influenced by afferent nerves 
from various parts of the body. Thus a ghastly 
sight, good news, an inflamed pericardium or 
peritoneum, may profoundly influence the pul- 
sations of the heart through its regulating cen- 
tres in the medulla. 

3. Inhibitory Action of the Vagus. — If the 
vagus of a frog or rabbit be excited by an inter- 
rupted current, the heart's action will become 
slower, and the blood- pressure in the arteries 
will be diminished ; or if the current be strong, 
it will be arrested in diastole. Section of the 



MEMORANDA OF PHYSIOLOGY. 91 

vagi is followed by an acceleration of the cardiac 
beats. If atropin be injected, even a strong 
current passed along the vagi will not diminish 
the cardiac beats. 

Reflex Inhibition. — If the intestines of a 
frog be struck sharply, or the mesenteric nerves 
stimulated, the heart is brought to a standstill 
in diastole. If the vagi are divided, or the 
medulla destroyed, this effect will not take 
place. The stimulus ascends to the medulla 
along the mesenteric nerves, and descends to 
the cardiac ganglia along the vagi. Irritation 
of other sensory nerves, as the posterior auricu- 
lar, will have a similar effect. 

4. Accelerator Nerves. — The sympathetic 
nerves which pass from the cervical cord to the 
last cervical and first dorsal ganglia, and from 
thence to the heart, are called the accelerator 
nerves. Stimulation of these nerves with the 
interrupted current causes quickening of the 
heart's action, and their division renders the 
heart's action slower. The blood-pressure in the 
arteries is not increased by exciting the acceler- 
ators, unless the peripheral resistance is in- 
creased by contraction of the arteries. These 
nerves seem to act by shortening both diastole 
and systole. 

II. Vaso-motor Centres. — The principal va- 



92 MEMORANDA OF PHYSIOLOGY. 

so-motor centre is situated in the medulla. Noth- 
ing- is known of this centre anatomically, its posi- 
tion having been determined by experiment. 
Excitation of the meduha of a frog with the 
interrupted current will cause the vessels in the 
web of a frog's foot (when seen beneath the mi- 
croscope) to contract. The same result can be 
witnessed in a rabbit by exposing a small artery. 
Section of the cord below the medulla causes 
the vessels to dilate. The latter experiment 
shows that the muscular fibre of the arteries is 
in a continual state of contraction or tonus. 
Various or subsidiary vaso-motor centres are 
situated in the spinal cord and various ganglia. 
Besides the vaso-motor, or rather vaso-constric- 
tor nerves, there are vaso-inhibitory or vaso- 
dilators. The vaso-motor fibres of the chorda 
tympani are vaso-dilators to the vessels of the 
submaxillary glands ; and the vaso-motor fibres 
of the nervi erigentes are vaso-dilators to the 
arteries supplying the erectile tissue of the penis. 
The vaso-motor centre can be also influenced by 
various afferent nerves ; this may occur through 
the higher nerve-centres, as in blushing ; excita- 
tion of the central end of various sensory nerves 
will bring about contraction of arteries ; while 
the vagus contains, especially in its superior 
laryngeal branch, fibres which excite and also 



MEMORANDA OF PHYSIOLOGY. 93 

fibres which, when stimulated, lead to inhibition 
of the vaso-motor centre. 

Action of Poisons, etc., on the Circulation. 

1. Nicotine, Curare, Conia paralyze the com- 
munications of the vagus with the inhibitory 
ganglia. Stimulation of the vagus is unable to 
slow the heart ; this effect, however, follows 
stimulation of sinus venosus. 

2. Huscarin and Jaborandi stimulate the 
whole inhibitory apparatus, and so cause the 
heart to stop in diastole. Atropia antagonizes 
them. 

3. Calabar lean also increases the excitability 
of the inhibitory mechanism, but will not stop 
it in diastole. 

4. Atropia, Hyoscyamine, Daturine paralyze 
the whole inhibitory mechanism. Excitation of 
the vagus and sinus venosus are without effect. 

5. Aconitia, Ver atria, Digitalin, Delphinia 
and Antiar affect the muscular fibre and arrest 
the heart in powerful systole. (See Hermann's 
kC Physiology," translated by Dr. Gamgee.) 



Section 5. 

THE LYMPHATIC SYSTEM. 



The lymphatics begin as capillary vessels in al- 
most every tissue of the body, and after passing 
through one or more of the lymph-glands, empty 
themselves either into the thoracic or right lym- 
phatic duct, and thence into the venous system. 

That portion of the lymphatic system which 
originates in the mucous membrane of the ali- 
mentary canal, takes up the chyle from the intes- 
tines during digestion, while it conveys lymph 
when digestion is not going on. 

Lymphatics have not been demonstrated in 
cartilage, tendon, the eyeball, the placenta, 
though it is probable they are not lacking. 

Structure. — The lymphatic capillaries closely 
resemble the ordinary capillaries of the body, 
their walls being formed of a single layer of 
epithelial cells with a sinuous outline. The 
lymphatic vessels resemble the veins, their inner 
coat consisting of a single layer of epithelial 



MEMORANDA C3* PHYSIOLOGY. VJ 

cells, arid a layer of longitudinal elastic fibres. 
The middle coat of circular muscular fibres mixed 
with elastic fibres. The external coat of con- 
nective tissue. 

Some of the lymphatic vessels entirely sur- 
round a small artery or vein ; the space between 
the artery and wall of lymphatic is called the 
perivascular space. 

They are provided with valves, which are 
placed so near to one another as to give them a 
beaded appearance when distended. 

Origin. — Two modes of origin — 

1. Plexiform. 

2. Lacunar. 

Plexiform. — Lymphatics begin as a network 
of capillaries beneath the skin, m.m. of stom- 
ach, surface of tendon and diaphragm, and 
other parts. Sometimes the plexuses are joined 
by small blind vessels, as in the intestine. 

Lacunar.— Lymphatics arise from the irreg- 
ular spaces which lie between the parts of 
which an organ is composed. The spaces be- 
tween the acini, or blood-vessels of a gland, are 
lined by an epithelium agreeing in character 
with that lining the lymphatics. The serous 
cavities, as the peritoneum, are large spaces 



- 44 



96 M35MOHANDA OF PHYSIOLOGY. 

from which the lymphatics arise by open mouths 
(the stomata). 

Terminations. — All the lymphatics of the 
body, sooner or later, empty themselves into 
the thoracic duct, except those of the right 
side of the head, neck, right thorax, right 
ripper extremities, right side of heart, which 
enter the right lymphatic duct. 

The thoracic duct commences opposite the 
second lumbar vertebra, by means of a dilated 
portion termed the receptaculum chyli, and ter- 
minates in the subclavian in the neck near its 
junction with the jugular. 

Lymphatic Glands are small bodies varying 
in size from a pea to an almond, placed in the 
course of the lymphatics. They are collected 
into groups in the mesentery, anterior and pos- 
terior mediastinum, elbow, axilla, neck, groin, 
and popliteal spaces. 

In structure they consist of a capsule of con- 
nective tissue and muscular fibre-cells, which 
sends fibrous septa or trabecular into the gland- 
substance. 

They have a hilus along one border, and are 
divided into a cortical and medullary portion, 
the latter occupying the centre of the gland, 
except at the hilus, where it comes to the sur- 
face. The fibrous septa which enter the gland 



MEMORANDA OF PHYSIOLOGY. 9/ 

divide it up into alveoli in the cortical portion, 
but form a closer network in the medullary. 
The alveoli are occupied by the true gland-sub- 
stance, but are separated from the fibrous septa 
by a narrow space, which is occupied only by 
retiform tissue, with nuclei at the intersections 
of their fibres, and which forms the lymph- 
channel, or sinus. 

The true gland-substance consists of retiform 
tissue, for the most part non-nucleated, its 
meshes being closely packed with leucocytes, 
and is traversed by blood-vessels. 

The afferent lymphatics which enter the 
gland at its convex border open at once into the 
lymph-sinus of the cortical part, pass on into the 
lymph-sinus of the medullary portion, and leave 
the gland at the hilus. In passing through the 
gland they come into close relation with the 
vessels ramifying in the gland-substance. 

The blood-vessels enter the gland at the hi- 
lus, and are distributed through the ^land-sub- 
stance ; the veins emerge also at the hilus. 

Functions. — Liq. sanguinis exudes from the 
capillary blood-vessels to supply the tissues 
with materials for their nutrition. The excess 
of liq. sanguinis thus supplied enters the lymph- 
atic capillaries, passes through the lymph - 
glands into the thoracic duct, and thence into 
7 



98 



MEMORANDA OF PHYSIOLOGY. 



the venous circulation. The liq. sanguinis that 
has passed out of the capillaries will accumulate 
in the connective-tissue spaces, or lacunse, from 
which the lymphatics arise. 

The lymphatics which arise in the villi of the 
smaller intestine are termed lacteals, and during 
digestion absorb fatty matters, and to a smaller 
extent soluble matters and albumen from the 
contents of the intestine. During the diges- 
tion of food, the columnar epithelium covering 
the villi may be seen to be distended with oil 
globules (though some observers assert the oil- 
globules pass between the cells), these globules- 
passing from the epithelium into the retiform 
tissue, and thence into the fine lacteal present 
in the villus. 

Lymph has been described as blood minus the 
red corpuscles. It is a yellow alkaline fluid of 
specific gravity 1045, and 6-7 per cent, of solids. 

It consists of — 



White corpuscles. 


Extractives. 


Elements of fibrin. 


Salts. 


Albumen. 


Water. 



It has been obtained for examination from 
the thoracic duct during a fasting period, or 
from some large lymphatic vessel. 

Chyle may be described as lymph plus fatty 






MEMORANDA OF PHYSIOLOGY. 99 

matters. It may be obtained from the thoracic 
duct during a period of digestion. It is an 
opaque milky fluid which clots when drawn 
from the duct : the clot exhibits a pink color. 
It contains 8-9 per cent, of solids. 
It consists of — 



White corpuscles. 


Albumen. 


Immature red ? 


Extractives. 


Fatty matters. 


Salts. 


Elements of fibrin. 


Water. 



Examined microscopically, white corpuscles 
are seen in abundance in chyle drawn from 
the upper part of the thoracic duct. Many of 
these white corpuscles are of a reddish color, 
and are probably being converted into red. 

The fatty matters consist of oil-globules of 
various sizes and finely divided matter of a 
granular appearance, which forms the molec- 
ular basis of chyle. Chyle undergoes changes 
in its passage from the villi to the thoracic 
duct ; these changes are effected through the 
agency of the mesenteric glands. They consist 
in a diminution of the molecular basis and an 
increase of the white corpuscles and elements 
of fibrin. Some of the white corpuscles appear 
to be of a reddish color. 



100 MEMORANDA OF PHYSIOLOGY. 

m 

Movements of the Lymph. 

1. Vis a tergo. Pressure of blood in the 
blood-vessels. 

2. Contraction of muscular fibres in their 
walls and in the villi. 

0. Compression by muscular action of volun- 
tary muscles. 

4. Vis a f route. Aspiration of thorax. 

1. If a ligature be applied to the thoracic 
duct, the chyle will tend to accumulate behind 
it, or if a tumor compress it the lacteals will 
become dilated and tortuous. This shows the 
existence of some vis a tergo. The liq. sanguinis 
leaves the capillaries under considerable pres- 
sure, and accumulating in the spaces of the 
tissues will readily pass into the lymphatic ves- 
sels. Increase of pressure in the arteries causes 
increased tension in the lymphatics. 

2. The muscular fibres in the walls of the 
lymphatic vessels act after the manner of the 
lymph-hearts in the frog. The contraction of 
the muscular fibres of the villi will assist in 
emptying the contents of the contained lacteal. 

3. Contraction of the voluntary muscles will 
compress the lymphatic vessels in the same way 
as the veins, driving the lymph forward, the 
valves preventing reflux. 



MEMORANDA OF PHYSIOLOGY. 101 

4. The enlargement of the chest during in- 
spiration sucks the blood in the large veins to- 
ward the heart ; the rapid motion of the blood 
in the subclavian over the orifice of the thoracic 
duct will tend to make the contents of the duct 
discharge into the vein, thus supplying the vis a 
fronte. 



Section 0. 

RESPIRATION. 

TRACHEA AND BRONCHL 

The walls of the trachea and two bronchi consist 
of several constituents — 

1. Connective tissue. 4. Submucous. 

2. Cartilages. 5. Mucous membrane. 

3. Muscular. 

1. The Connective Tissue coat forms an ex- 
ternal sheath for the trachea, surrounding and 
joining together the cartilages. 

2. The Cartilaginous Rings are incomplete 
behind, being C-shaped, are 16-20 in number, 
consist of hyaline cartilage, and serve to main- 
tain a certain amount of rigidity in the walls. 

3. The Muscular Layer is only present be- 
hind, connecting the tips of the cartilages to- 
gether, and is also present behind in the inter- 
vals between the rings. Its fibres belong to the 



MEMOKANDA OF PHYSIOLOGY. 103 

unstriated variety, and serve by their contrac- 
tion to diminish the diameter of the tube. 

4. The Sub-mucous coat contains besides 
connective tissue numerous longitudinal elastic 
fibres, which may readily be seen on examina- 
tion from within the tubes. There are also nu- 
merous racemose mucous glands. 

5. The Mucous Membrane is lined by co- 
lumnar ciliated epithelium, beneath which is 
situated more or less lymphoid tissue, resem- 
bling that of the solitary glands of the intes- 
tines. The cilia work toward the outlet of the 
trachea and help to expel mucus and foreign 
matter. The mucous membrane and muscular 
fibres are supplied with branches of the pneumo- 
gastric nerves. 

The two bronchi exactly resemble the trachea 
in structure, the right having 6 to 8, the left 9 to 
12 incomplete cartilaginous rings. 

'Lungs (weight, right 24 ozs., left 21 ozs.). 
The lungs are surrounded by the pleurae, the 
smooth surfaces of the latter diminishing fric- 
tion during the movements of respiration. In 
shape they are conical, the apex projecting into 
the root of the neck, the base resting upon 
the arch of the diaphragm ; the inner surface 
being flattened where the bronchi and vessels 
enter. 



104 MEMORANDA OF PHYSIOLOGY. 

The lungs consist of — 



1. 


Lobes. 


4. Infundibula. 


2. 


Lobules. 


5. Air-sacs. 


8. 


Bronchi. 


6. Blood-vessels and nerves. 



1. The Lobes are the primary divisions, the 
right having three, the left two. 

2. Lobules. — The lobes are divided into lob- 
ules of various sizes, their outline being most 
readily seen on the cut surface of foetal lungs ; 
they are separated by fine connective tissue. 
In struc ure th^y resemble a lung in miniature, 
having a bronchus, branch of pulmonary artery 
and ve n. The bronchus divides and redivides 
several times in the lobule, till it terminates in 
the small dilatations of the infundibula. The 
branch of the pulmonary artery entering the lob- 
ule divides in a similar manner, then breaks up 
into capillaries surrounding the air-sacs. 

3. The Bronchi, on entering the lung, divide 
and redivide, each of the smaller divisions en- 
tering a lobule. In structure they resemble the 
trachea, with some modifications. The carti- 
lages in the larger tubes form complete rings, 
but as the tubes get smaller the cartilages form 
incomplete rings, consisting of small plates in 
the walls arranged in a circular manner, and fi- 
nally are wanting altogether in tubes of fa in. 



MEMORANDA OF PHYSIOLOGY. 105 

in diameter. The muscular fibres entirely sur- 
round the tubes, and may be traced into the 
finest ramifications. The elastic fibres extend to 
tubes of the smallest size and become continu- 
ous with the elastic fibres forming the walls of 
the infundibula. The ciliated epithelium ceases 
at the entrance into the infundibula. 

4. Infundibula are the small sacculated dila- 
tations in which the smallest bronchi terminate. 
Their walls are formed of elastic tissue, and the 
many small dilatations of sacculi in their walls 
form the air- sacs. 

5. Air-sacs are about T ^jj in. in diameter ; 
their interior, communicating with the bronchi, 
is lined by a single layer of squamous epithe- 
lium, while their walls are surrounded by a 
plexus of capillary blood-vessels. The contained 
air is thus brought into close relation with the 
blood in the capillaries, and an interchange of 
gases readily takes place. 

6. The Pulmonary Arteries accompany the 
bronchi and finally break up into the fine capil- 
laries surrounding the air-sacs from which the 
veins arise. 

The Bronchial Arteries, two or three in num- 
ber, arise from the aorta, and are distributed to 
the bronchi, lymphatic glands, connective tissue, 
and mucous membrane. The right bronchial 



106 MEMORANDA OF PHYSIOLOGY. 

vein entars the vena azygos, and the left the 
superior intercostal vein. 

Mechanism op Respiration.— The lungs 
are compound elastic bags, communicating with 
the outside air, and suspended in a semi-dis- 
tended state in an air-tight cavity with movable 
walls. When the cavity of the thorax is en- 
larged by the contraction of certain muscles, the 
lungs become distended by drawing in air. 
When the muscles relax, the lungs tend to col- 
lapse, expelling most of their contained air — a 
result due in part to the contraction of the elas- 
tic tissue they contain, and also to the recoil of 
the elastic rib cartilages. 

Inspiration. — The chest enlarges in three 
directions, viz., downward, forward, and later- 
ally. The enlargement downward is affected 
by the contraction of the diaphragm. At rest 
the diaphragm presents a convex surface to the 
thorax ; in contracting this surface becomes 
natter, the floor of the chest is lowered, the 
cavity of the thorax enlarged, and air enters to 
distend the lungs. The contraction of the dia- 
phragm tends to press the abdominal viscera 
downward and causes the walls of the abdomen 
to project during inspiration. 

The ant ero -lateral enlargement is effected by 
raising the ribs. A vertebrosternal rib has two 



MEMORANDA OF PHYSIOIiOGT. 107 

movable joints, the posterior where the head 
articulates with the sides of the bodies of the 
vertebrae, and the anterior at the junction of the 
costal cartilage with the sternum. The anterior 
end occupies a lower position than the posterior, 
so that the rib is in more or less of an oblique 
position. When the anterior ends are raised, 
the sternum will be pushed forward, and the an- 
terioposterior diameter of the chest enlarged. 
When the ribs are raised by the external inter- 
costal muscles, the angles which they make with 
the sternum become more obtuse, and the chest 
enlarged in the transverse diameter. 

Muscles of Inspiration — Normal. — The ribs 
are raised by the contraction of certain muscles 
in normal inspiration, namely external intercos- 
tals, that portion of the internal intereostals be- 
tween the cartilages, levator es costarum and 
scalenL The diaphragm is also constantly in 
action during ordinary inspiration. 

Labored Inspiration. — When breathing be- 
comes difficult other muscles come into play. 

The sealeni are strongly contracted, so as to 
fix the first rib. The serratus posticus superior 
helps to raise the upper 4 or 5 ribs. The serra- 
tus posticus inferior and quadratuslumborum 
help to fix the lower four ribs, and thus increase 
the power of the diaphragm. When still further 



108 MEMOKANDA OF PHYSIOLOGY. 

efforts are necessary, the arms and shoulders 
are fixed, the serratus magnus (scapula to upper 
8 or 9 ribs), pectoralis major (humerus to 2d to 
•6th costal cartilages) , pectoralis minor "(coracoid 
process to 3d, 4th, and 5th ribs), latissimus 
dor si (in part, e.g., humerus to lower ribs), help 
to elevate the ribs and enlarge the chest. 

Expiration — Normal. — Ordinary easy expi- 
ration is effected by the elastic recoil of the lungs 
and costal cartilages. During inspiration the 
elastic tissue of the lungs is put on the stretch, 
and the costal cartilages and ribs are abnormally 
bent ; both tend to return to their unstretched 
condition, and in doing so force out the inspired 
air. In this act they are aided by the internal 
intercostals. 

Forced Expiration. — The abdominal mus- 
cles, by compressing the abdominal contents, 
force the diaphragm upward and depress the 
sternum and lower ribs. The quadratus lum- 
borum, serratus posticus inferior, and sacro-lum- 
balis will depress the ribs, and assist in expira- 
tion if the diaphragm is not contracting. 

Summary. — Respiration is carried on under 
ordinary circumstances by the diaphragm and 
external intercostals which enlarge the chest and 
allow air to be sucked into the lungs, followed 
almost immediately by the recoil of the elastic 



MEMORANDA OF PHYSIOLOGY. 109 

lungs and ribs forcing out the air so inspired. 
But when there is more than the ordinary ve- 
nous condition of blood in the system, greater ef- 
forts must be made to supply the lungs with oxy- 
gen, and muscles not ordinarily employed in the 
effort must be brought into play. The arms and 
scapulae are fixed by seizing hold of some ob- 
ject, and by bringing into action the trapezius, 
levator anguli scapulae and rhombei, so as to 
make firm attachments for serratus magnus, 
pectorales and latissimus in their efforts to raise 
the ribs. Labored expiration in like manner 
brings extra muscles into play. In labored res- 
piration the nostrils are expanded by the dila- 
tor nares during inspiration, and resume their 
original size during expiration. The glottis is 
widely open during inspiration, while it is nar- 
rowed during expiration. These movements of 
the glottis occur during ordinary breathing, but 
are exaggerated during difficult breathing. 

Rhythm and Number of Respirations. — 
Each respiratory act consists of three periods — 
(1) inspiration, (2) expiration, (3) pause. Inspi- 
ration is usually shorter than expiration, the 
open glottis readily admitting the air. Expira- 
tion is more prolonged, the glottis being smaller, 
the vocal chords being approximated, and leav- 
ing only a narrow chink. The number of res- 



110 MEMORANDA OF PHYSIOLOGY. 

pirations amounts to 15 or 18 per minute, or 1 
to every 4. 5 or 4 beats of the pulse. 

Vital Capacity. — The vital capacity of the 
chest is the amount of air which can be expired 
from the chest after taking the deepest possi- 
ble inspiration, and is equal to about 225 to 230 
cu. in. 

The Tidal Air is the air which is constantly 
passing in and out of the chest during calm 
breathing, and amounts to 25 to 30 cu. in. 

The Complemental Air is the air which can 
be drawn into the chest after taking an ordinary 
inspiration ; it amounts to about 100 cu. in. 

The Reserve Air is the air which can be ex- 
pelled at a forcible expiration over and above 
the tidal air ; it equals about 100 cu. in. 

The Residual Air is the air which still re- 
mains after every effort has been made to 
empty the lungs ; it is equal to about 100 cu. in. 

( Complemental=100 cu. in. 

Total vital ca- J TWal = 25 - 30 cu. in. 

pacity. ( Reserve =100 cu. in. 

Residual =100 cu. in. 

The lungs normally are never quite empty, 
even after the most forcible expiration, but still 
contain about 100 cu. in. This may in part be 
expelled in some diseases, as in whooping-cough, 



MEMORANDA OF PHYSIOLOGY. Ill 

the lung in places being collapsed. In other 
diseases, as in emphysema, the lungs contain a 
greater amount of residual air than normally, 
the chest becoming more or less barrel -shaped. 



Changes of the Air in Respiration. 

1. Temperature. The expired is warmer 
than the inspired air ; the temperature depend- 
ing to some extent upon the temperature of the 
inspired air, and the rate and depth of the 
breathing. 

2. The expired air is saturated with aqueous 
vapor. 

3. The expired air contains 4 to 5 per cent, 
less oxygen, and about 4 per cent, more car- 
bonic acid gas. 

O 
Inspired air 21 

Expired air 16 

A certain amount of oxygen does not reappear 
in the expired air, in the form of carbonic acid. 
During 24 hours an adult man gives out about 
800 grammes (12,300 grains) of C0 2 , containing 
218 grammes (3,300 grains) of C, and consumes 
about 700 grammes (11,000 grains) of O. 



N 


C0 2 


79 


.04 


79.5 


4.3 



112 



MEMORANDA OF PHYSIOLOGY. 



4. In addition to carbonic acid, the expired 
air contains ammonia, and other unknown sub- 
stances of a poisonous or deleterious nature. 
An atmosphere containing .08 per cent, of C0 2 , 
with the accompanying impurities, is unwhole- 
some, while .1 per cent, of C0 2 , with propor- 
tional amount of impurities, is very injurious. 

Changes in the Blood. 

1. It is cooled. 

2. It loses watery vapor. 

3. It gains oxygen (8 to 12 percent, per vol.). 
The amount of oxygen in the blood rising from 
about 12 to 20 per cent, per vol. 

4. It loses carbonic acid (7 per cent, per vol.). 
The amount of C0 2 in the blood falling from 46 
to 39 per cent, (see p. 63). 



Circumstances Affecting the Excretion of 
Carbonic Acid. 

1. Muscular Exercise. 

2. Food. 

3. Age. 

4. Disease. 

1. Muscular exercise increases the amount of 
carbonic acid exhaled. E. Smith found that 
there was expired — 



MEMORANDA OF PHYSIOLOGY. 113 

Per minute. 

During sleep 4.99 grains. 

Lying down 5.91 

Walking 2 miles an hour.. 18.10 " 
Walking 3 miles an hour. . 25.83 " 
Exercise on treadmill 44.97 " 

2. The amount exhaled in the expired air is 
increased by food, especially starchy foods. 

3. The amount exhaled increases up to the 
thirtieth year, and diminishes after forty-five. 

4. Many diseases, as the fevers, increase the 
amount of C0 2 in the expired air. 

Abnormal Respiration. —If the blocd in 
the body contains more than an ordinary amount 
of oxygen, no efforts to breathe will take place ; 
this condition is called Apnoea. The ordinary 
natural condition of respiration is termed Eup- 
ncea. As soon as the blood in the body be- 
comes more venous than ordinarily, in conse- 
- quence of the amount of oxygen sinking below 
normal, the respiratory movements become 
quicker, and both inspiratory and expiratory 
efforts are increased by bringing extra muscles 
into play. This condition of difficult breathing 
is termed Dyspnoea. As the blood becomes 
more and more deficient in oxygen, the respi- 
ratory efforts become more labored, the expira- 



114 MEMOBAKDA OF PHYSIOLOGY. 

tory movements becoming', more marked than 
the inspiratory. The expiratory efforts become 
convulsive in character, and the whole muscles 
of the body presently take part in the convul- 
sions. In the last stage the convulsions cease, 
coma sets in, the pupils dilate, the conjunctivae 
are insensible, while at intervals respiratory ef- 
forts, chiefly inspiratory, are made. The term 
asphyxia is applied to the later stages follow- 
ing dyspnoea, when insensibility has set in. 
1 Thus in oxygen starvation three stages may be 
witnessed. (1) A stage of dyspnoea, character- 
ized by increased respiratory movements, both 
inspiratory and expiratory. (2) A convulsive 
stage, in which expiratory efforts are most 
marked. (3) A stage of coma, marked by in- 
sensibility, and slow, deep inspiratory efforts. 

When the trachea of a dog is suddenly oc- 
cluded, the first stage lasts about one minute ; 
the second stage also lasts a minute ; in the third 
stage some two or three minutes elapse before 
death occurs. 

The Circulation in Asphyxia. — During the 
inspiratory and expiratory efforts of the first 
and second stages the blood pressure rises, but 
during the third stage' it sinks till death ensues. 
The rise of blood pressure is brought about by 
constriction of the smaller arteries, the result 



MEMORANDA OF PHYSIOLOGY. 115 

of tlieir carrying venous blood ; the left side of 
the heart becomes full ; the increased respira- 
tory movements assist the return of blood to 
the right side of the heart, so that the cavities 
on both sides of the heart become distended. 
The distended heart at first beats more quickly, 
then more slowly and forcibly, and finally be- 
coming exhausted from being continually sup- 
plied with venous blood, ceases altogether. The 
heart continues to beat for some time afte r 
the respiratory movements have ceased. At a 
post-mortem examination, it will be found there 
is a distended right side, but an empty left, 
rigor mortis having caused contraction of the 
left ventricle. 

Asphyxia due to Oxygen Starvation. — 
When an animal is made to inhale nitrogen only, 
the exit of carbonic acid is not interfered with, 
yet all the effects of dyspnoea and asphyxia 
ensue, a result due to the absence of oxygen in 
the blood. If an animal breathe an atmosphere 
rich in carbonic acid and with plenty of oxygen, 
the breathing becomes deeper at first ; this 
afterward passes off, and the animal becomes 
unconscious, without any convulsive move- 
ments, the carbonic acid acting as a narcotic 
poison. 

The Nervous Mechanism of Respiration. — 



116 MEMOKANDA OF PHYSIOLOGY. 

Breathing is a reflex act, capable of being 
modified by the will. The nerve-centre is situ- 
ated in the medulla, the afferent nerves are the 
vagi, the efferent nerves are the phrenics, inter- 
costals, etc. Respiration continues in the ab- 
sence of consciousness and after the removal of 
the brain above the medulla ; but destruction 
of a certain small portion of the medulla below 
the vaso -motor centre causes the movements at 
once to cease. This spot is called the n&ud 
vital. The centre is influenced by impulses 
from without or within — a dash of cold water 
in the face, a cold bath, an emotion, venous 
blood in the pulmonary vessels, all call it into 
action. The centre is probably automatic as 
well as reflex ; section of the vagi, thereby inter- 
rupting the channel by which the afferent im- 
pulses reach it from the lungs, while interfering 
with the respiratory act, does not stop it. Auto- 
tomatic impulses descend from the centre along 
the efferent nerves. Probably the venous blood 
circulating through the centre itself supplies the 
stimulus . 

Section of Vagi. — If one vagus is divided, 
respiration is slower ; if both are divided it be- 
comes very slow, while each respiration is fuller 
and deeper, so that the amount of carbonic acid 
given off is not much altered. During life the 



MEMORANDA OF PHYSIOLOGY. 117 

terminal fibres of the vagi are stimulated by the 
venous blood in the pulmonary capillaries, the 
stimulus travelling upward to the medulla. 
The more venous ^the blood, the more intense 
the stimulus transmitted upward, and the 
greater the number of muscles brought into 
play. If the central end of a divided vagus be 
stimulated by the interrupted current, the res- 
pirations are quickened ; if the stimulus is in- 
creased, the diaphragm is brought into a tetanic 
condition. Stimulation of the central end of 
the superior laryngeal causes a slowing of the 
respiratory movements to take place, the dia- 
phragm becoming relaxed if the stimulus is 
sufficiently intense. 

Coughing consists in a deep inspiration, fol- 
lowed by a closure of the glottis, and finally a 
sudden forcible expiration, which bursts open 
the glottis and forces out any mucus or foreign 
matter presen fc in the air-passages. The afferent 
impulses travel along the superior laryngeal 
nerve from the larynx, or the vagi from the 
bronchi, lungs, or pleura, or the auricular branch 
distributed to the outer ear. 

Sneezing closely resembles coughing, except 
that the expiratory blast is driven through the 
nose, the soft palate and anterior pillars of 
the fauces shutting off the mouth from the 



118 MEMORANDA OF PHYSIOLOGY. 

pharynx ; the afferent impulses travelling along 
the fifth. 

Hiccup is caused by the spasmodic action of 
the diaphragm, causing a sudden inspiration 
and closure of the glottis. The afferent im- 
pulses travel along the vagi from the stomach. 

Effects of Respiration on the Circulation. — 
If a tracing be taken by means of a kymograph 
connected with the carotid of a dog, it will be 
seen that, in addition to the small oscillations 
produced by the intermittent action of the 
heart, there are larger waves which correspond 
with the respiratory movements. The summit 
and base of the waves do not exactly correspond 
with either inspiration or expiratioD. At the 
beginning of inspiration arterial pressure, as 
shown by a tracing, is falling ; it soon begins to 
rise, and reaches its maximum socn after the 
commencement of expiration. 

If a dilated vein, often seen in the neck, is 
watched, or the vein of a dog be laid bare, it 
will be noticed that during inspiration the vein 
collapses, and during expiration it is distended. 
It appears therefore that inspiration lowers the 
tension in the venous system, and increases 
tension in the arterial, though the latter effect 
does not reach its maximum till expiration has 
begun. These effects are produced in the fol- 



MEMORANDA OF PHYSIOLOGY. 119 

lowing manner : The expansion of the cavity of 
the chest during inspiration not only draws air 
down the trachea, but tends also to suck the 
blood in the veins and arteries immediately out- 
side the chest to the heart. Thus death may 
be caused by an injury to the veins of the neck, 
air being drawn in. The arterial system, with its 
high pressure, is but little affected ; not so the 
blood in the large veins ; during an inspiration, 
blood in the innominates and inf. v. cava will 
rush toward the right side of the heart ; more 
will pass through the pulmonary vessels, the 
left ventricle becomes more distended, and its 
beats more forcible, increasing tension in the 
arterial system, though, as before remarked, the 
maximum does not occur till after the com- 
mencement of the following expiration. In 
expiration the negative pressure in the veins 
caused by inspiration is removed, the flow of 
blood in the veins is no longer assisted, less 
blood enters right side of heartland conse- 
quently less blood enters left side, and arterial 
pressure falls. Expiration, however, tends to 
increase arterial tension by direct pressure on 
the thoracic aorta, but to so small an extent 
that its effects may be disregarded. 



Section 7- 

ANIMAL HEAT. 

Heat is generated throughout the body where- 
ever oxidation processes are going on. When- 
ever arterial blood comes in contact with active 
protoplasm, in the glands, muscles, or tissues, 
heat is produced. The haemoglobin gives up 
its oxygen to the carbon and hydrogen present 
in the blood or tissues, forming C0 2 and H 2 0, 
and generating heat. 

Cold-blooded Animals are those whose oxi- 
dation processes are feeble, so that their tem- 
perature is but slightly raised above, and varies 
with that of the medium in which they live. 
All classes of animals are cold-blooded except 
birds and mammals. The temperature of the 
frog is only slightly above that of the air, 
though it is 1° or 2° C. higher during the breed- 
ing season. Some fishes and snakes have a tem- 
perature of 10° C. above the medium in which 
they live. In the cold-blooded animals, the 
amount of heat generated within their tissues 



MEMOEANDA OF PHYSIOLOGY. 



121 



is slight, and their temperature will vary with 
the season and the circumstances under which 
they are placed. 

Warm-blooded Animals are those in which 
the oxidation processes are vigorous, so that they 
maintain a temperature considerably above that 
of the surrounding medium. In man, the aver- 
age temperature is 37° C. (98.6° F.) (axilla) ; in 
some birds, as the swallow, it is 44° C. (Ill 
P.), the more active birds having a higher tem- 
perature than mammals. This temperature re- 
mains nearly constant, notwithstanding the 
changes of temperature in different seasons and 
climates. Slight elevations of temperature take 
place when the external air is considerably 
raised, as in a Turkish bath (100.6° F. in a bath 
of 120° F.). In disease there is often a notable 
rise of temperature ; in scarlatina or typhus it 
may rise to 41.2' C. (106° F.) or higher, in 
acute rheumatism 43.3° C. (110° F.), and in one 
case of fracture of the spine to 50° C. (122° F.) 
Such elevations are alarming. In other dis- 
eases, as in uraemia and cholera, it sinks "below 
normal. 

The temperature of 98.6° F. is the resultant 
of two sets of processes. 

I. Those by which heat is gained. 

IT. Those by which it is lost. 



122 MEMORANDA OF PHYSIOLOGY. 

I. Heat is gained to the Body — 

1. Wherever arterial blood comes in contact 
with active protoplasm, chemical changes taking 
place. 

2. By friction of the muscles. 

3. By ingestion of hot liquids and foods. 

II. Heat is lost to the Body — 

1. By means of the skin — evaporation of the 
perspiration, radiation, and conduction, 77.5 per 
cent. 

2. By the lungs — evaporation of the water of 
respiration, and warming expired air, 20 per 
cent. 

3. By escape of urine and fasces, 2.5 per cent. 

The warmest blood in the body is that of the 
hepatic vein. The liver is the largest gland in 
the body, and its cells are constantly engaged in 
effecting chemical changes in the blood circu- 
lating through that organ. Blood returning 
from active muscles is warmer than the blood 
supplied to them. The brain, spleen, and pan- 
creas, when in an active state, are a source of 
heat to the blood. 

The circulation of the blood insures an equa- 
ble temperature throughout the body by distrib- 
uting the heat. But in order to maintain an 



MEMORANDA OF PHYSIOLOGY. 123 

average temperature of 98.6° P. under different 
circumstances as regards external heat, the 
amount of blood supplied to different parts must 
be regulated.. The amount of heat lost by the 
skin will depend upon the amount of blood cir- 
culating through the vessels near the surface of 
the body. If the cutaneous arteries are di- 
lated, an increased amount of heat will be 
lost by evaporation of the perspiration poured 
out, as well as by radiation and conduction, and 
less blood is supplied to the internal organs 
where heat is produced. Thus, if the body be 
exposed to cold, the vessels of the skin are con- 
tracted and less perspiration poured out, and 
more blood is supplied to the liver and internal 
organs, and more heat generated as well as less 
lost. But if the body be exposed to heat, as in 
a Turkish bath, the cutaneous vessels are dilated, 
perspiration is poured out and evaporated, more 
heat is lost and less generated in the internal 
organs. 

The exact conditions under which the in- • 
creased amount of heat is produced in fevers or 
acute rheumatism are not well understood. 

One of the functions of the vaso-motor system 
is to regulate the size of the arteries and there- 
fore the amount of blood supplied to a part. 
Increased supply of blood to a part will increase 



124 MEMOKANDA OF PHYSIOLOGY. 

the tissue change and thereby the temperature, 
or if it be near the surface, its temperature will 
be increased from a greater supply of blood, 
warmer than itself. Section of the sympathetic 
in the neck is followed by redness and heat of 
the corresponding ear and side of the face, a 
difference of 4° to 6° C. being noticed. 

Injuries to the central nervous system, as in 
effusion of blood in the brain or some injury to 
spinal cord, are often followed at first by a lower- 
ing, probably from shock, and then in a few 
hours an increased temperature ranging up to 
108° F. or more. In hemiplegia, the tempera- 
ture of the paralyzed side is generally one or 
two degrees higher than the sound side, but in 
old cases of paralysis the paralyzed limbs 'are 
often cooler, apparently from defective circula- 
tion. The vaso-motor centre being situated in 
the medulla, any interference with its action 
will be likely to alter the temperature of the 
body by interference with the blood-supply. 



Section 3. 

FOOD. 

Food may be divided into — 

1. Nitrogenous. 

2. Hydro-carbons, or fats. 

3. Carbo-hydrates, or starches. 

4. Inorganic. 

1. Nitrogenous. — N enters largely into the 
composition of the tissues ; it must, therefore, 
enter the body in the form of food, to replace 
the loss which is continually taking place. 
The nitrogenous principles present in the food 
are — 

Albumen Syntonin Vegetable albumen. 

Fibrin Globulin do. fibrin (gluten). 

Casein Gelatin do. casein (legumin). 

Vitelline Chondrin. 

These principles undergo digestion in the 



126 MEMORANDA OF PHYSIOLOGY. 

stomach and intestines, and are converted into 
the peptones. The peptones are absorbed by 
the portal vein, and pass throngh the liver be- 
fore entering the general circulation. The 
changes they undergo in the liver are not well 
understood. 

Destiny of Nitrogenous Foods. — 1. Devel- 
opment and renovation of the tissues. 2. To 
assist in the formation of the secretions. 3. 
Force production. 

1. During infancy, the rapid cell -growth re- 
quires abundant nutriment in the form of albu- 
minous matters. Throughout the whole life there 
is a continual wear and tear of the tissues ; each 
individual cell has a period of activity and a sub- 
sequent death ; albuminous material is required 
to replace the cells which have perished. Thus, 
the epithelial cells on the surface of the skin are 
constantly being worn away, and require re- 
newal from the deeper cells. The red corpus- 
cles, the secreting epithelium of the various 
glands, after remaining in an active state for a 
certain period, perish, and fresh ones are needed 
to replace them. 

2. The secretions of the body, as the gastric 
and pancreatic juices, are constantly using up 
albuminous material to form their active prin- 
ciples. 



MEMOKANDA OF PHYSIOLOGY. 127 

3. Force-production. — Liebig maintained that 
nitrogenous food was utilized to build up the 
proteid tissues, as muscle and other forms of 
protoplasm, and that urea, uric acid and their 
allies, arose solely from the breaking- up of 
these tissues, while non-nitrogenous food was 
used exclusively for the maintenance of heat or 
was stored as fat. The mechanical energy of 
the body being derived from the oxidation of 
the muscles, or formed nitrogenous material. 
If this were true, the amount of muscular ex- 
ercise would be proportional to the amount of 
urea appearing in the urine. This has been fre- 
quently disproved. It has been shown by 
Parkes, Fick, Wislicenus and others, that the 
urea is very slightly increased by muscular ex- 
ercise, not in proportion to the work done, 
while the amount of urea in the urine has been 
shown to be proportional to the amount of al- 
buminous food ingested. Probably some por- 
tion of the albuminous food taken is split up, 
the N escapes from the system as urea, CON 2 Hi, 
leaving roughly about two-thirds of its original 
weight, consisting of CHO, to be stored as fat 
or glycogen, or oxidized in the system, supply- 
ing mechanical energy or heat, and escaping as 
C0 2 and H 2 0. Thus : 



128 MEMORANDA OF PHYSIOLOGY. 

Albumen=C=53.5 Urea=C=20. 

=H= 7 =H= 6.6 

=N=15.5 =N=46.6 

=0=22 -0=26,6 
= S = 1.6 
=P= A 

100 100 

Nitrogenous foods have not all the same die- 
tetic value. The albuminoids, gelatin, and 
chondrin are inferior to albumen. Their inges- 
tion is followed by an increased quantity of 
urea in the urine. But life cannot be main- 
tained for a long time on gelatin alone, or in 
combination with fats or starches. Probably 
no part of the gelatin compounds are utilized 
in the nutrition of the tissues, but are split up 
into urea and some fatty body. 

Dynamic Value of Nitrogenous Foods. — 
Albumen, when completely oxidized, is con- 
verted into NHo, C0 2 , and H 2 0. It is not com- 
pletely oxidized in the body, being converted 
into urea, uric acid, C0 2 , etc. , some (about one- 
seventh) therefore of its energy is unexpended. 

One gramme of beef") 
muscle, when com- | 5,103 grammes of water 
pleteiy oxidized, will J- 1° C., or 2,161 kilo- 
give out sufficient | grammes, 1 metre ; 
heat to raise J 



MEMORANDA OF PHYSIOLOGY. 129 

One gramme of beef ) 4,368 gramme-degrees, 
muscle, as oxidized >• or 1,850 kilogramme- 
in the body ) metres. 

2. Hydro-carbons, or Fats, are neutral 
bodies derived from both animal and vegetable 
foods. They consist of olein, palmitin, and 
stearin. Olein and palmitin are met with both 
in animal and vegetable products ; olein is fluid 
at ordinary temperatures ; palmitin has a semi- 
fluid consistence. Stearin is a solid fat, is found 
only in animal products, and exists largely in 
suet. They all have glycerine for a base in 
combination with the corresponding fatty acids, 
oleic, palmitic, and stearic. The fats are re- 
markable for the small quantity of they con- 
tain ; thus in palmitic acid (Ci 6 , H32, 2 ) the 
amount of is about 12 per cent, of its weight, 
leaving from 80 to 90 per cent, available for 
force -production . 

Digestion of Fats. — The gastric juice dis- 
solves the connective tissue, binding together 
the fat vesicles and sets free the fat. The fatty 
matters are emulsified in the small intestine by 
the action of the pancreatic juice, and in a 
lesser degree by the other secretions, and for 
the most part enter the lacteals, though a cer- 
tain proportion, which has possibly become sa- 
ponified, enters the portal vein. 
9 



130 MEMORANDA OF PHYSIOLOGY. 

Destiny of Fats. — The fats are utilized in the 
body for force-production, either immediately 
or are stored as adipose tissue to be used when 
required. They therefore serve for the main- 
tenance of heat and performance of muscular 
work. The capacity of a material for force- 
production depends upon the amount of unoxi- 
dized C and H it contains, and of all alimentary 
substances fats take the highest place. Ex- 
perimentally, Frankland has shown that the 
actual heat developed by the various alimentary 
substances when burnt in O is as follows : 

1 gramme beef fat, 9,069 gramme -degrees. 

a butter, 7,264 " " 

" beef muscle, 5,103 " " 

" arrowroot, 3,912 u u 

That is to say, 1 gramme, or 1 lb. of fat when 
burnt, will give off heat sufficient to raise 9,069 
grammes, or 9,069 lbs. (about 4 tons) of water, 
1° C. Whereas the same amount of arrowroot 
would, when burnt, only raise 3,277 grammes of 
water 1° C. 

It is found that the inhabitants of arctic 
regions readily devour all kinds of fat, while in 
the tropics the food of the iDhabitants consists 
largely of farinaceous and saccharine matters. 
The force generated by the oxidation of the 



MEMORANDA OF PHYSIOLOGY. 131 

hydro-carbons is available for muscular work. 
A large amount of muscular work ,can be per- 
formed on a fatty or starchy diet. During mus- 
cular exercise, the amount of CO L » given off at 
the lungs varies according to th*e work done ; 
thus, 5 grains per minute during sleep, and 25 
grains per minute walking at the rate of three 
miles an hour. 

The amount of mechanical work obtainable 
from the oxidation of — 



1 gramme beef fat = 3,841 
" butter = 3,077 

" beef muscle == 2,161 
" arrowroot = 1,657 J 



kilogramme 
metres. 



That is, the force derivable from the oxidation 
of 1 gramme of fat, is sufficient to raise 3,841 
kilogrammes one metre. (1 kilogramme-metre 
=7.232 foot-pounds.) 

The products of the combustion of fat are 
H 2 and C0 2 . Animal life cannot long be main- 
tained on a non-nitrogenous diet. Dogs fed on 
fat, or fat and starches, emaciate and die. 
Nitrogenous food is required to renew the tis- 
sues, which become wasted and worn during the 
processes of life. 

3. Carbo-hydrates or Amyloids comprise 



16'4 MEMORANDA OF PHYSIOLOGY. 

starch, cane sugar, grape sugar, milk sugar, 
glycogen. Chemically these bodies differ from 
the fats in containing a smaller quantity of un- 
combined carbon and hydrogen. The O exist- 
ing in sufficient quantity to form water with all 
the H present, starch (C 6 Hi O 5 ), and grape 
sugar (CeHioOe). 

Starch is met with in the vegetable products. 
It is prepared for absorption by being converted 
into grape sugar in the mouth and small intes- 
tine. Cane sugar and glycogen are converted 
into grape sugar in the stomach and intestines. 
Milk sugar (CioHosOi'i-hH^O) and grape sugar 
(CoH 12 06-f H^O) are readily absorbed by the 
portal vein and submitted to the action of the 
liver. Here some change takes place. Sugar 
injected into the jugular vein rapidly appears in 
the urine ; injected into the portal it does not, 
unless in large quantity. The grape sugar is 
converted in the liver into glycogen (C 6 H 12 6 
— H 2 0=C2Hio0 5 ) and probably also into fat. 

It is uncertain whether the glycogen is recon- 
verted into sugar and oxidized in the system, or 
whether it enters the system as glycogen or 
some similar body. In any case it is oxidized, 
being converted into C0 2 and H 2 0, and giving 
rise to heat, and supplying force for the per- 
formance of work. 



MEMORANDA OF PHYSIOLOGY. 133 

4. Inorganic Materials. — Various salts 
exist in the body in combination with the or- 
ganic materials that form the tissues. The chief 
salts consist of calcium, sodium, potassium, 
magnesium, and iron, in combination with chlo- 
rine, phosphoric, carbonic, and sulphuric acids. 

DIETETICS. 

Experience proves that a mixed diet is the 
best to maintain the body in health. Dogs will 
not live on hydrocarbons or carbo-hydrates 
alone. Too much nitrogenous food leads to an 
excessive amount of urea and uric acid, and 
throws increased work on the excretory organs. 

Milk, the food of early life, may be taken as 
a typical illustration of a natural combination 
of the varieties of food. 

Milk contains — 

Cow. Woman. 
Nitrogenous matters (casein and 

albumen) 4.1 3.35 

Butter 3.9 3.34 

Milk sugar 5.2 ) 

Salts 8f 3 * 77 

Water 86 89.54 



100 100 
Cow = 14 per cent, solids. 
Woman = 10 to 11 per cent. 



134 MEMORANDA CF PHYSIOLOGY. 

Diet for Moderate Work.— The normal diet 
for a man in health can only be arrived at by 

experience. Taking the average of a large num- 
ber of healthy persons, it has been found that 
the following diet will suffice: — 

Dry food. Ozs. 

Albuminous matter 4.5 

Fatty matter 3. 

Carbo-hydrates ' 14.2 

Salts 1.0 



Thus about 23 ozs. of dry solid food are con- 
tained in this standard diet, about £ of which is 
nitrogenous. If we reckon that 50 per cent, of 
ordinary food is water, these 23 ozs. will corre- 
spond to 46 ozs. of ordinary solid food. In addi- 
tion about 50-80 ozs. of water are taken. The 
force-producing value of this standard diet is 
nearly 4,000 foot-tons. 

The standard diet will necessarily be altered 
under different conditions. 

It is said that an Esquimaux eats about 20 
lbs. of flesh and oil daily, and men working 
heavily necessarily require more than when at 
rest. 



MEMORANDA OF THYSIOLOGY. 135 

Diet for Idleness: 

Ozs. 

Albuminous matter 2.5 

Fats 1.0 

Carbohydrates 12.0 

Salts 5 

This diet will keep a man alive, but is not suf- 
ficient if he performs any work. 

Hard-Work Diet. — The average dietary of a 
laborer performing hard work has been calcu- 
lated at — 

Ozs. 

Nitrogenous matter 5.08 

Fat 3.9 

Carbo-hydrates 22.2 

Mineral 9 

Dynamic value 5,232 foot-tons. 

Taking the model diet for ordinary men — 
Ozs. N. C. 

Nitrogenous matter... 4.5 310 1,068 

Fat 3.0 1,024 

Carbo-hydrates 14.25 2,768 

316 grs. 4,860 grs. 

It appears, therefore, that a man on ordinary 
diet and doing an ordinary amount of work re- 
quires 300 grs. of N. and 4,800 grs. of C. 

The ratio of the quantities is 1-16. In albu- 
men the ratio is 1-3.5. Hence, if albumen 



133 



MEMORANDA OF PHYSIOLOGY. 



alone were used, and the 300 grains of N. were 
supplied, there would be a deficiency of C. , and 
if the 4,800 grains of C. were supplied, there 
would be more N. than required. In bread the 
ratio is as 1-30 ; so that if bread alone were 
used, there would be a superfluity or deficiency 
of either N. or C. Two pounds of bread and 
three-quarters of a pound of meat will fulfil the 
above conditions, though it will better do so if 
1-2 ozs. of butter be added. 



Table Showing Amount of Different Constituents 

in Some Foods, 

In 100 parts. 



Articles. 


Water. 


Albu- 
minates. 


Fats. 


Carbo- 
hydrates. 


Salts. 


Beef and mutton . 
Bacon 


75 
15 

49.1 

78 

15 

40 

10 

15 

15 

74 

73.5 

36.8 

80.7 

6 

3j 


15 

8.8 
29.6 
18.1 
11 

8 

5 

12.6 
22 

1.5 
13.5 
33.5 

4 
.3 


8.4 

73.3 

.2 

2.9 

2 

1.5 

.8 

5.6 

2 

.1 

11.6. 

24.3 

3.7 

91 


70.3 

49.2 

83.2 

63 

53 

23.4 

5 

96.5 


16 
2.9 


Salt beef 

White fish 

Flour 

Bread 


21.1 
1 

1.7 
1.3 


Kice 

Oatmeal 

Peas (dry) 

Potatoes 

Eggs 


.5 

3 
2.4 

1 
1 


Cheese 


5.4 


Milk 


.6 
2.7 


Sugar 


.5 







(After Parkes.) 



MEMORANDA OP PHYSIOIX)GY. 



137 



Table Showing Carbon and Nitrogen in Various 
Foods. 





Grains per pound. 




Carbon. 


Nitrogen. 


Split peas 


2,699 
3,016 
2,563 
2,693 

2,700 

2,831 

1,975 

2,660 

2,732 

769 

599 

3,344 

1,900 

1,854 

5,987 

871 

6,456 

2,955 


248 


Indian meal 


120 


Barley meal 


68 


Rye meal 


86 


Seconds flour 


116 


Oatmeal 


136 


Bread 


88 


Pearl barley ».,..... 


91 


Rice 


68 


Potatoes 


22 


Milk 


44 


Cheese 


306 


Mutton 


189 


Beef 


184 


Bacon 


95 


White fish 


195 






Sugar 









(Letheby. ) 

Effects of Starvation.— The most prominent- 
symptoms are first, pain in the epigastrium, re- 
lieved by pressure ; this subsides in a day or 



138 MEMOBANDA OF PHYSIOLOGY. 

two, and is succeeded by a feeling of weakness 
and of intense thirst. The countenance be- 
comes pale, the body exhales a peculiar fetor, 
and the bodily strength rapidly fails. The tem- 
perature is lower than normal. The mental 
powers exhibit similar weakness: first, stupidity, 
then imbecility, which sometimes is succeeded 
by maniacal delirium. Life terminates by gradu- 
ally increasing torpidity, or, occasionally, by a 
convulsive paroxysm. 

With entire abstinence from food and drink, 
death occurs in from eight to ten days. The 
Welsh fasting girl lived eight days. This time 
may be prolonged if water can be obtained, or 
if surrounded by a warm, damp medium. 

The loss during starvation falls most heavily 
on the fat, next the glandular organs, then the 
muscles, the heart and brain being affected 
least. The post-mortem examination shows ex- 
treme emaciation and complete absence of fat. 
All the organs, with perhaps the exception of 
the brain, are bloodless ; the coats of the intes- 
tines thin and empty of contents. The gall- 
bladder full, the bile staining the surrounding 
parts. The body rapidly passes into decom- 
position. 



Section 9. 

DIGESTION. 

THE TEETH. 

Two sets of teeth make their appearance dur- 
ing the life of man. 

I. The temporary, or milk teeth (20). 
II. The -permanent set (32). 

I. The Temporary Set appears during the 
first two years of life. They consist of two in- 
cisors, one canine, and two molars, in each half- 
jaw, making twenty in all. They appear in the 
following order, the numbers referring to the 
months : 

Incisors, 5, 11. Canines, 13, 20. Molars, 12, 30. 

There are no bicuspids in the temporary set. 
They resemble the permanent teeth in general 
form, but are considerably smaller. 

II. The Permanent Set.— The first six 
months of life are passed without any teeth ; by 
the end of the second year the milk teeth have 



140 MEMORANDA OF PHYSIOLOGY. 

all appeared, and these begin to be replaced by 
the permanent set at the sixth year, and are 
completely replaced by them at the twelfth or 
thirteenth year ; the teeth being completed by 
the eruption of the wisdom teeth at the age of 
about twenty -one. When complete there are 
thirty- two, there being two incisors, one canine, 
two bicuspids, and three molars, in the half of 
either jaw. They replace the temporary set in 
the following order, the numbers referring to 
the years of age : 

Incisors, 1] 8. Canine, 11. Bicuspids, 9, 10. 
Molars, 6, 12, 21. 

The Incisors (8) are arranged side by side in 
the front of the jaws. They have a single long 
conical fang, and a sharp chisel- shaped edge, 
for dividing the food. 

The Canines (4) are placed singly, next to the 
lateral incisors. Their fangs are single, large, 
and conical, compressed laterally, and cause 
a prominent ridge in the alveolus of the jaw. 
The crown is more pointed than in the incisors. 

The Bicuspids (8) are arranged four in each 
jaw. The fangs are bifid at their apices, more 
marked in the upper and second bicuspids, and 
are grooved laterally. The crown is compressed 
from before backward, and is surmounted by 
two tubercles, or cusps, separated by a groove. 



MEMORANDA OF PHYSIOLOGY, 141 

The Molars (12) are arranged three in each 
jaw, behind the bicuspids. They have from 
two to three fangs. In the two anterior molars 
of the upper jaw they are three in number, 
two external and one internal. The two an- 
terior molars of the lower jaw have two fangs, 
one anterior and one posterior. In the third 
molar, or wisdom tooth, the fang is irregular 
and single. The crowns of the molar teeth are 
cuboidal in form, rounded on each lateral sur- 
face, and flattened in front and behind. The 
upper molars have four cusps at the angles of 
the grinding surface, separated by a crucial de- 
pression ; the lower molars have five cusps. The 
molars, from the great breadth of their crowns, 
are suitable for grinding and pounding the food. 

Structure. — Minute anatomy — 

A tooth consists of a crown, which projects 
from the gum, a root or fangs, which are fixed 
in a socket in the bone, and a short intermediate 
neck. Each is supplied with an artery and 
jierve, and has a central cavity filled with a soft 
vascular sensitive substance, the pulp. 

1. Pulp. 3. Dentine. 

2. Crust a petrosa. 4. Enamel. 

1. The pulp occupies the central cavity of 



i 



142 MEMORANDA OF PHYSIOLOGY. 

the tooth, and consists of fine connective tissue, 
nucleated cells, blood-vessels, and nerves. The 
cells, or odonto blasts, are said to send fine»pro- 
cesses into the dentine tubules. The arteries 
are derived from the internal maxillary and 
nerves from the fifth pair. 

2. The crusta petrosa, or cement, covers the 
fang of the tooth, its place being' taken below 
by the enamel which covers the crown. Tn 
structure it resembles bone, containing lacunas 
and canaliculi, but they are larger and more 
irregular. 

3. The dentine forms the principal mass of 
the teeth, being protected by the crusta petrosa 
and enamel, and hollowed out in the centre to 
form the pulp cavity. It is somewhat harder 
than bone, and differs from it in structure. ' It 
is penetrated by numerous fine tubes, giving it 
a striated appearance beneath the microscope, 
the tubes appearing dark and the matrix trans- 
parent. The tubules open into the pulp cavity, 
and radiate to the periphery, giving off small 
branches. They are nnjo in. in breadth and 
have a distinct wall, the dental sheath. As the 
dentine is sensitive, it is possible they may con- 
vey nerve-fibres as well as prolongations of the 
cells of the pulp cavity. The matrix is homo- 
geneous. 



MEMORANDA OF PHTSIOIiOGY. 143 

4. The enamel is very hard and covers the 
crown. It is made up of microscopic prisms 
arranged side by side ; these prisms are six- 
sided and aifoo m - m diam., and are marked at 
intervals by transverse lines. 

Chemical Composition. — The hard tissues 
of the teeth, like bone, consist of animal matter 
and mineral matter : the former yields gelatin 
on boiling, and exists in different amounts in the 
tissues — 

Bone 33 per cent, animal matter.' 

Crusta petrosa 30 " " " 

Dentine 28 M " " 

Enamel 3.5 " " 

The mineral matter consists of calcic phos- 
phate and carbonate, magnesic phosphate and 
calcic fluoride. 

Development. — At the seventh week of in- 
fra-uterine life, a groove appears on the surface 
of the jaws, which involves the soft embryonic 
tissues of the jaw as well as the Malpighian 
layer of the epithelium. It was called by 
Goodsir the primitive dental groove. This down- 
growth of epithelium forms the common enamel 
germ, and from it the enamel is developed. 
From the bottom of this groove, which has be- 
come flask-shaped in section, papillae, twenty 



144 MEMORANDA OF PHYSIOLOGY. 

in number, arise. These papillae become en- 
closed in sacs, and form the future tooth by 
becoming vascular, and lime salts being de- 
posited. 

The ten anterior permanent teeth in each 
jaw are formed from small grooves behind the 
milk teeth, which are converted into cavities, 
and are termed w l cavities of reserve. ' ' A little 
papilla forms in each cavity, and forms the 
future permanent tooth. The six posterior 
teeth, or molars, arise from extension of the 
primitive groove backward, and have been 
named u posterior cavities of reserve" 

THE TONGUE. 

The tongue is a muscular organ which plays 
an important part in articulation, mastication, 
and deglutition; it is covered with mucous 
membrane, containing the organ of taste. 

The mucous membrane surrounds the tongue, 
and forms various folds, as it is reflected to 
neighboring parts. In the middle line, on the 
under surface, is the f rsenum lingua?, and on the 
upper surface, behind, are the three glosso- 
epiglottidean folds. In structure it resembles 
the skin, having a cutis, with papillae covered 
by a stratified flattened epithelium. The under 
surface of the tongue is smooth, the upper sur- 



ftrEMORAXDA OP PHYSIOLOGY. 145 

face, especially the anterior two-thirds, is rough, 
from the presence of numerous special papillce. 
There are three kinds of papilla?, circumvallate, 
fungiform, filiform. 

The Circumvallate papillae are eight to ten 
in number, situated at the back of the tongue, 
arranged in the form of the letter V with the 
apex backward. They are rounded in form, and 
Y-f hi. in width ; their attached ends being some- 
what narrower than their free ends, and are 
situated in a cup-shaped depression, which sur- 
rounds them like a trench. They are beset with 
numerous secondary papilla?, which are covered 
by the flattened stratified epithelium that lines 
the tongue. Embedded in the sides of the 
papilla? are numerous flask-shaped bodies com- 
posed of modified epithelium cells called taste- 
buds, with which the nerve- endings are con- 
nected. The papilla? are supplied with an 
arterial twig and nerve. 

The Fungiform papilla? are smaller than the 
preceding, and are scattered over the dorsum, 
more particularly at the sides and apex. They 
are of a deep red color, narrow at their attached 
ends, and broad and rounded at their free ex- 
tremities. They contain some of the taste-buds, 
and are supplied with nerves and capillaries. 

The Filiform papilla? cover the anterior two- 
10 



148 MEMORANDA OF PHYSIOLOGY. 

thirds of the dorsum of the tongue : they are 
long and slender, and of a whitish tint. They 
are covered by a peculiar kind of epithelium, 
which is dense and imbricated, and possesses 
many hair-like processes. 

Glands. — There are numerous small racemose 
glands, resembling minute salivary glands in 
structure, beneath the mucous membrane ; 
some of them open into the fossa surrounding 
the circumvallate papillae, and secrete a thin 
saliva and mucus. 

The Tonsils are two rounded bodies situated 
between the anterior and posterior pillars of the 
pharynx. In structure they consist of lymphoid 
tissue ; some twelve or fifteen recesses, or crypts, 
open on the anterior surface. 

MASTICATION. 

The first stage in the digestion of food con- 
sists in its mastication in the mouth. It is 
crushed between the teeth and rolled about by 
the movements of the tongue to mix it thor- 
oughly with the saliva. 

The movements of the muscles are voluntary, 
though from use they become habitual in char- 
acter, and will continue when the influence of 
the will is withdrawn, and the attention directed 
elsewhere, provided there is a sensation of 



MEMORANDA OP PHYSIOLOGY. 147 

hunger and food within reach. The mouth is 
opened by the anterior belly of the digastric, 
mylo-hyoid and genio-hyoid muscles. It is shut 
by the combined action of the masseter, tem- 
poral, internal pterygoid muscles. The external 
pterygoids acting together thrust the jaw for- , 
ward : it is retracted by the posterior fibres of 
the temporal. The grinding movement is per- 
formed by the alternate actions of the external 
pterygoids. The tongue on the inner, and the 
buccinator on the other side, press the food be- 
tween the molars, and the action of the zygo- 
matici helps to keep the buccinator and mucous 
membrane of the cheek from being included be- 
tween the teeth. 

THE SALIVA. 

The Saliva is secreted by three glands, paro- 
tid, sub-maxillary, sub-lingual, and also by the 
smaller glands beneath the mucous membrane 
of the tongue and cheeks. 

Structure of Salivary Glands. — They are 
compound racemose glands, and consist of nu- 
merous lobules, each supplied with a duct and 
blood-vessels, and bound together by connective 
tissue. The duct divides and redivides in the 
lobule until its smaller divisions enter a cluster 
of saccules, or acini. These acini are lined by 



14:8 MEMOEAXDA OF PHYSIOIiOGY. 

spheroidal epithelium with well-marked nuclei ; 
the cells occupy nearly the whole of the acinus, 
leaving a very small lumen in the centre. The 
ducts are lined by columnar epithelium. 

Composition. — Saliva is a viscid, frothy alka- 
line fluid, specific gravity 1002-1007, and con- 
taining about | per cent, of solid matter. From 
80 to 60 fluid ozs. are secreted in twenty-four 
hours. 

It contains — 

1. Mucin. 4. Salts.* 

2. Ptyalin. 5. Water. 

3. Albumen. 

Microscopically, epithelium cells, mucus and 
salivary corpuscles are seen. 

Ptyalin or Diastase is an albuminous body of 
the nature of a ferment. 

The salts include potassium sulphocyanide ; 
the latter salt is recognized by its giving a red 
coloration with ferric chloride, which is unal- 
tered by HC1, and destroyed by mercuric chlo- 
ride HgCl 2 . 

Uses. — 1. Liquefies starch foods, and changes 
the starch into dextrin and maltose. 2. Mois- 
tens the food, and therefore assists in mastica- 
tion and deglutition. 3. Administers to the 
sense of taste by dissolving the food. 



MEMORANDA OF PHYSIOLOGY. 149 

Probably at least two-thirds of our food con- 
sists of starch. Starch in its uncooked state 
resists the action of the saliva, but when cooked 
it is digested with facility. If saliva be added 
in moderate quantity to a jelly or paste made 
from corn flour or other form of starch at a 
temperature of the body, in a few moments the 
jelly becomes thin and watery ; this change 
takes place prior to any chemical change. 
Shortly a distinct action will be obtained with 
Fehling's solution for sugar. Later on the re- 
action becomes abundant. If a solution of iodine 
be added from time to time, it will be noted 
that at first a pure blue color is obtained show- 
ing the presence of starch, later a deep violet 
tint, then a red coloration, a brown colora- 
tion, and finally the iodine ceases to give any 
reaction, but the amount of sugar will go on 
increasing for a time after the iodine has ceased 
to color the solution. These reactions are 
very complicated ; starch is converted into sev- 
eral different kinds of dextrin before the final 
change into sugar is reached. 

Starch is converted into maltose (C12H22O11), 
a sugar which differs from grape-sugar (CeHisOe) 
in having less sweetening power less readily re- 
duces cupric oxide, but exercises more rotatory 
power on polarized light. The starch molecule 



150 MEMOKANDA OF PHYSIOLOGY. 

is probably 10(Ci 2 H 2 o0 10 ). The final result is 
represented by : 

10(C 12 H 20 O 10 ) + 8H 2 8(C 12 H aa O u ) + 2(C 12 H 20 O 10 ) 
soluble siarch water = maltose dextrin 

Innervation of the Salivary Glands. — The 

secretion of saliva is a reflex act, due to the 
excitation of food placed in the mouth, or to 
mental stimuli induced by the sight or thought 
of food. 

The arteries supplying the gland are influ- 
enced by two opposing nerves, (1) the vaso- 
motor, which narrow their calibre and diminish 
the supply of arterial blood to the gland, and 
therefore lessen secretion ; (2) the vaso-inhib- 
itory, which antagonize the vaso-motor, and 
hence increase alike the blood- supply and the 
secretion of the gland. The vaso-motor are de- 
rived from the sympathetic, the vaso-inhibitory 
for the sub-maxillary gland from the chorda 
tympani, passing through the sub-maxillary 
ganglion, and for the parotid, the lesser super- 
ficial petrosal, passing through the otic gan- 
glion. 

The presence of food in the mouth excites 
the terminal fibres of the gustatory (5th) and 
glosso-pharyngeal nerves ; the sensation is trans- 
mitted to the medulla ; it is reflected along the 



MEMORANDA OF PHYSIOLOGY. 151 

chorda tympani, which, by inhibiting the sym- 
pathetic, dilates the blood-vessels, and increases 
the functional activity of the sub-maxillary 
gland, and saliva is poured out. According to 
Heidenhain, the chorda tympani contains fibres 
which directly stimulate the epithelium, as well 
as fibres which inhibit the sympathetic, the 
former being paralyzed by atropin. 

In the dog the parotid secretion is the most 
watery and the sublingual the most viscid. Ac- 
cording to Bernard, the sub -maxillary adminis- 
ters to the sense of taste, the parotid being con- 
nected with mastication, and the sublingual 
with deglutition. 

DEGLUTITION. 

Deglutition is a complicated act by means of 
which food passes from the mouth into the 
oesophagus without any part of it being allowed 
to enter the nasal cavity or the larynx. It is 
usually divided into three acts — 

1. The passage of food to the back of the 
mouth. 

2. Its passage across the orifice of the larynx. 

3. Its seizure by the constrictors and its pas- 
sage through the oesophagus to the stomach. 



152 MEMORANDA OF PHYSIOLOGY. 

1. The bolus having been prepared, the tongue 
carries it back through the anterior pillars of 
the fauces, the movement being effected through 
the agency of the stylo-glossus and intrinsic 
muscles of the tongue. 

2. The soft palate is raised by the action of 
its muscles, and assisted by the contraction of 
the upper part of the superior constrictor, shuts 
off the cavity of the nose from the pharynx. 
The larynx is raised behind the hyoid bone by 
the action of the stylo-pharyngeus and thyro- 
hyoid, the vocal chords are approximated and 
the epiglottis closely fitted over the rima glot- 
tidis by the action of the depressor. The pas- 
sages both into the nares and larynx being 
closed, the descending bolus passes over the 
root of tongue, epiglottis, and beneath a roof 
formed by the contraction and approximation 
of the palato-pharyngeal muscles, is seized by 
the constrictors, and propelled into the oeso- 
phagus. 

Deglutition is a reflex act. 

Afferent Nerves, — Glosso-pharyngeal and 
branches of 5th. 

Nerve Centre. — In the medulla. 

Efferent. — Pharyngeal branch of vagus, hypo- 
glossal, glosso-pharyngeal, and facial. 



MEMORANDA OF PHYSIOLOGY. 153 

THE (ESOPHAGUS. 

The (Esophagus is the muscular tube extend- 
ing 1 from the pharynx to the stomach. It con- 
sists of three coats — 

1. External, or muscular. 

2. Middle, or submucous. 

3. Internal, or mucous. 

1. The External coat consists of an outer 
layer of longitudinal and an inner layer of cir- 
cular muscular fibres. The muscular fibres in 
the upper part are striated, but are gradually 
replaced by non-striated in the lower half. 

2. THe Submucous coat consists of connec- 
tive tissue, and contains some mucous glands. 

3. The Mucous coat is pale in color, and 
when the oesophagus is contracted is thrown 
into longitudinal folds. In structure it resem- 
bles the skin, having a cutis, papillas, rete 
mucosum, lined by stratified flattened cells. 

The food is propelled along the oesophagus by 
the peristaltic action of its muscular walls. It 
is a reflex act : the afferent and efferent nerves 
are supplied by the vagus. Food accumulates 
in the oesophagus of an animal in which the 
vagus is divided below the pharyngeal branches, 
the animal being able' to swallow the food, but 



154 MEMOEANDA OF PHYSIOLOGY. 

the oesophagus fails to pass it on into the stom- 
ach from paralysis of its mu&cular walls. 

THE STOMACH. 
Structure. — Four coats — 

1. Serous. 3„ Submucous. 

2. Muscular. 4. Mucous. 

1. The Serous coat is derived from the peri- 
toneum ; it invests the whole organ, except at 
the curvatures. 

2. The Muscular coat contains fibres of the 
non-striated variety. Longitudinal, best marked 
along* the curvatures and near the pylorus. 
Circular, forming a complete layer over the 
whole extent of stomach, becoming thick and 
strong at the pylorus and forming the sphincter. 
Oblique, scattered over the surface and con- 
tinuous with circular of oesophagus. 

3. The Submucous, coat consists of a layer of 
connective tissue between the muscular and 
mucous. 

4. The Mucous coat is a smooth pink mem- 
brane, which is loosely attached to the tissue be- 

• neath, and when the stomach is empty is thrown 
into rugae. The mucous membrane contains a 
fine layer of muscular tissue, the muscularis 
mucosal, internal to which are the tubular glands. 



MEMOKANDA OF PHYSIOLOGY. 155 

Tubular Glands. — On examining a section of 
stomach stained with logwood or aniline, ren- 
dered transparent with glycerine, the tubular 
glands are seen parallel to one another and 
closely crowded together, with their blind ex- 
tremities toward the muscularis mucosae, and 
opening on the surface of the mucous mem- 
brane. Their length varies from -£$ to -^ in. 
and diam. 3^0 to §~oo m - m breadth. Two dif- 
ferent kinds of glands are distinguished ; some 
in larger numbers near the pyloric orifice are 
lined throughout with columnar epithelium, 
and are supposed to secrete mucus and are 
called mucous glands. The peptic glands have 
columnar epithelium at their mouths only, the 
rest of the gland being lined by two different 
sets of cells ; those at the circumference of the 
tubule resting on the basement membrane, being 
oval in shape, are called ovoid or peptic, and 
another set, occupying a more central position, 
are cubical in shape and are termed central 
cells. 

Delicate lymphoid tissue may be seen in 
places in the mucous membrane, resembling the 
solitary glands of the intestine. 

The Gastric Juice is a thin, colorless acid 
fluid of specific gravity 1,001 to 1,010, contain- 
ing i to 1 per cent, of solids in man. The daily 



156 MEMORANDA OF PHYSIOLOGY. 

arnonnt varies, an average being* 22-24 pints 
( 1 o -1 4 litres) . It contains : 

1. Pepsin. 4. Mucin. 

2. A curdling ferment. 5. Salts and water. 

3. Hydrochloric acid (free). 

About two thirds of the solid matter consists 
of peptones and pepsin and one -third of salts. 
Amount of free HC1 = .02 per cent. 

Artificial gastric juice is best prepared by dis- 
secting off the mucous membrane of the stom- 
ach of a pig, cutting it into small pieces and di- 
gesting it in glycerine for a few days, filtering 
and adding fresh mucous membrane. This may 
be repeated several times. Each time the gly- 
cerine will take up a fresh quantity. A little 
of the glycerine extract added to 2 per cent, 
solution of HC1 will form an active artificial 
gastric juice. 

Action of gastric juice. — It has no action on 
starches, cane-sugar, or fats. It simply dis- 
solves the connective tissue binding the fat- 
vesicles together and setting free the fats. The 
characteristic action of gastric juice is its action 
on albuminous compounds converting them in- 
to the peptones. Proteid substances first swell, 
become semitransparent, and then dissolve. 
There are several different bodies included un- 



MEMORANDA OF PHYSIOLOGY. 157 

der the peptones, such as metapeptone, para- 
peptone, dyspeptone, but they closely resemble 
one another in properties. They differ from al- 
bumen in the following ways : 

1. They readily diffuse through animal mem- 
branes. 

2. They are not coagulated by heat or nitric 
acid. 

3. They are not precipitated by acetic acid 
and ferrocyanide of potassium. 

4. They give a pink color on the addition of 
caustic potass and a trace of cupric sulphate or 
TTehling's solution. 

They resemble albumen in being pirecipated — 

1. By tannic acid. 

2. By lead acetate. 

The part that pepsin plays in digestion is that 
of a ferment resembling the action of ptyalin in 
the saliva. Pepsin is nob destroyed in the act 
of digestion, its digestive power appears to be 
infinite. Yet if more and more fibrin be added 
to artificial gastric juice, it will at last remain 
undissolved, the arrest of digestion being due to 
accumulation of the peptones and want of acid. 
For if the liquid be diluted and more acid added, 
digestion will recommence. The activity of the 
pepsin is greatest at a temperature of 30°-50° 



158 MEMOKANDA OF PHYSIOLOGY. 

C. (86°-112° F.). It is completely destroyed by 
boiling. 

Gastric juice contains a distinct ferment which 
has the property of curdling milk (Roberts). 

Digestion of the Stomach. — If a quantity 
of milk be introduced into the stomach of a 
rabbit and the animal killed an hour after and 
laid in a warm place for twenty-four hours, the 
walls of the stomach will probably be found di- 
gested. If a portion of the stomach of a dog be 
ligatured, the wounded stomach sewn up, and 
the dog allowed to live a few hours, the portion 
included in the ligature will be digested. The 
stomach itself is not digested during life, in 
consequence of the circulation through its walls 
of alkaline blood. 

Secretion of Gastric Juice. — The stomach 
has two secretions, one thick, tenacious, and 
alkaline -the gastric mucus; the other, thin, 
acid, and watery — the gastric juice proper. 
The former is secreted during fasting, while 
the latter is only secreted when food or fluid 
enters the stomach. Saliva or alkalies, pepper, 
alcohol, excite the secretion of gastric juice. 
Their action is reflex : the vagus is probably 
the afferent nerve, which, acting on the medulla, 
inhibits the sympathetic and dilates the blood- 



MKVIOKANDA OF PHYSIOLOGY. 159 

vessels supplying the glands ; the efferent im- 
pulses descending along the splanchnics. 

Movements of the Stomach. — Food during 
digestion in the stomach is kept in motion by 
the peristaltic action of its walls. By the con- 
traction of its muscular fibres currents are set 
up in its contents, the food travelling along the 
large curvature and returning by the lesser, 
while as digestion proceeds certain portions 
are passed through the pylorus into the duo- 
denum. 

Vomiting is a reflex act by which the con- 
tents of the stomach crre expelled through the 
oesophagus and mouth. Very different circum- 
stances may give rise to vomiting. 

1. Irritation of the terminal fibres of the 
vagus from the presence in the stomach of cer- 
tain substances as ipecacuanha, or a catarrhal 
state of the mucous membrane. , 

2. Irritation of the terminal fibres of different 
branches of the vagus or sympathetic, as in 
tickling the fauces, an inflamed peritoneum, an 
enlargement of uterus, as in the vomiting of 
pregnancy. 

3. Direct irritation of the nervous centres, as 
in tumor of the brain or circulation through the 
nerve-centres of certain substances, as apomor- 
phia, 



160 MEMORANDA OF PHYSIOLOGY. 

4. Vomiting- may also be induced by disgust- 
ing* smells, sights, or tastes. 

The afferent nerves depend upon the cause ; 
they may be vagus, sympathetic, first, second, 
etc. 

The nerve-centre, probably in the medulla. 

The efferent nerves, phrenic, and nerves to 
abdominal muscles. 

Mechanism of vomiting. — Peristaltic waves 
run from the pylorus to the cardiac end of the 
stomach, the cardiac aperture being fiimly 
closed. Then a deep breath having been taken, 
the diaphragm fixed, and glottis closed, the car- 
diac sphincter is suddenly opened by fibres con- 
tinuous with the longitudinal fibres of the oeso- 
phagus, the abdominal muscles contract, and 
the stomach being fixed by the diaphragm, its 
contents are expelled. 

Structure of Small Intestine.— The small in- 
testine commences at the pylorus and empties 
itself into the caecum, and is about twenty feet 
in length. It is divided into three portions, 
the duodenum occupying the first ten or twelve 
inches, the upper two-fifths of the remainder 
being jejunum, and the lower three-fifths ileum. 

It has four coats — serous, muscular, areolar, 
mucous. The Serous entirely surrounds the 
gut, except where the vessels enter. The Mus« 



i 



MEMOKANDA OF PHYSIOLOGY. 161 

cular consists of two layers, external longitudi- 
nal and internal circular. The Areolar is a 
loose connective- tissue layer between the mu- 
cous and muscular. The Mucous lines the in- 
testine, and in the upper part of the jejunum is 
thrown into numerous transverse folds, called 
the valvule conniventes, which are permanent 
and extend about two-thirds of the way round 
the intestine. They increase the absorbing sur- 
face and help to delay the contents of the intes- 
tine. The mucous coat is separated from the 
areolar by a thin layer of muscular fibres, the 
muscularis mucosa?, and, like the stomach, is 
lined by columnar epithelium. It is provided 
with — 

1. Villi. 

2. Brunner's glands. 

3. Crypts of Lieberkuhn. 

4. Solitary glands. 

5. Peyer's glands. 

6. Lymphoid tissue and vessels. 

1.* The Villi are small processes of mucous 
membrane which exist from the pylorus to the 
ileocascal valve, and give the inner surface of 
the intestine a velvety appearance. They are 
about 4^ to ^o m - m length and are closely 
set together. They consist of an external layer 



162 MEMORANDA OF PHYSIOLOGY. 

of columnar epithelium, a basement membrane, 
a plexus of capillary vessels, a lacteal vessel, a 
few muscular fibre-cells prolonged from the mus- 
cularis mucosae and retiform tissue. 

2. Brunner's Glands are small compound 
glands existing in the duodenum. They consist 
of clusters of acini in connection with a minute 
duct, which opens on the surface. 

3. The Crypts of Lieberkuhn are minute 
blind tubes which exist in every part of the in- 
testine opening between the villi. They are 
lined by columnar epithelium and are xlo m - to 
■3 Jo in. in length. 

4. The Solitary Glands are small white 
bodies about the size of millet seeds scattered 
through the intestine. They consist of lym- 
phoid tissue surrounded by a plexus of capilla- 
ries. 

5. Peyer's Glands are groups of glands re- 
sembling the solitary glands in structure. They 
are situat°d for the most part in the lower por- 
tion of the ileum. The groups are oblong and 
placed lengthways in the intestine opposite to 
the attachment of the mesentery. 

6. Lymphoid tissue is found in various 
places in the submucous tissue, in addition to 
that of the solitary and Peyer's glands. 



MEMOKANDA OF THYSIOLOGY. 163 

SECRETIONS POURED INTO THE INTES- 
TINE. 

Bile is an alkaline, golden yellow fluid of a 
bitter taste and specific gravity 1018, and con- 
taining about fourteen prr cent, solid matter. ( 
If it remain long in the gall-bladder it becomes 
viscid from the presence of mucus. From thirty 
to forty ounces are secreted in twenty-four 
hours. 



Composition : 


1. 


Mucin. 


2. 


Bile pigments. 


3. 


Sodium salts of bile acids. 


4. 


Cholesterin. 


5. 


Lecithin. 


6. 


Salts and Aq. 



Bile-pigments. — The yellow color of the bile 
of man and carnivora is due to Bilirubin ; the 
green color of herbivora and that of man after 
oxidation is due to Biliverdin. A small quantity 
of Biliprasin may be present. 

Gmeliri's Test. — When strong yellow nitric 
acid is added to bilirubin, or human bile, on a 
white plate, a succession of colors is produced, 
in the order of the colors of the spectrum — 
green, blue, violet, indigo, and red. If biliver- 



161 MEMORANDA OF PHYSIOLOGY. 

din be used the same result occurs, the first 
color being- blue. In applying the test to urine, 
care must be taken to notice the colors succeed 
one another in their right order, as the presence 
of indican may cause green, blue, and yellow 
colors. 

Bilirubin may be prepared from dog's bile by 
acidulating with acetic acid and shaking with 
chloroform ; the chloroform dissolves the bili- 
rubin, and on evaporation leaves the pigment of 
a red color. 

Biliverdin may be obtained by allowing an 
alkaline solution of bile to become green by ex- 
posure to the air. The bilirubin is oxidized and 
biliverdin formed, precipitating by HC1, dissolv- 
ing in alcohol and evaporating. Bilirubin is be- 
lieved to be derived from haemoglobin during 
its passage through the liver. It seems to be 
identical, with the hsematoidin found in old 
blood-clots. 

Bile acids are taurocholic and glycocholic 
acids. These acids are composed of cholic acid 
in combination with taurin and glycocine. 

Pettenkofer } s Test — A small quantity of dilute 
bile is mixed with a few drops of sugar (cane- 
sugar) and strong H 2 S0 4 added ; the solution 
becomes first cherry red, then of a purple color. 
Some other organic substances give a similar 



MEMORANDA OF PHYSIOLOGY. HjD 

color, but may be distinguished by the spectro- 
scope. 

Preparation. — Bile is rubbed up with animal 
charcoal and dried at steam heat ; it is thus ren- 
dered colorless. The bile acids are then dis- 
solved out by absolute alcohol and precipitated 
by ether, as silky needles, which readily take up 
moisture and form a syrupy fluid. 

Cholesterin can be obtained best from gall 
stones by boiling with alcohol and filtering 
while warm ; white rhombic crystals of cho- 
lesterin form. 

Uses of Bile. 

1. Slight action in converting starch into 
sugar. 

2. Assists in emulsifying and saponifying fats. 

3. Assists in the absorption of fats. 

4. Increases peristaltic action. 

5. Prevents putrefactive changes in intes- 
tines. 

The action that bile exerts in converting starch 
into sugar and in emulsifying fat is slight. 
Mucous membrane, wetted with bile, allows 
minute globules of fat to pass readily through 
it, and in this way it aids the absorption of 
fat. It increases the peristaltic action of the 



166 MEMORANDA OF PHYSIOLOGY. 

intestine, thus aiding in the propulsion for- 
ward of the contents of the intestine- It 
stimulates the contraction of muscular fibres 
of the villi emptying the lacteal, and forcing 
onward its contents. It checks putrefactive 
changes. In jaundice, where the bile is pre- 
vented from flowing into the intestine, there is 
a tendency to constipation and flatulence. 

Bile is being constantly secreted and accumu- 
lates till required in the gall-bladder. When 
the acid contents of the stomach enter the 
duodenum a reflex action is set up, leading to 
the contraction of the gall-bladder, and pouring 
out of bile into the intestine. 



THE PANCREAS. 

Structure. — The pancreas belongs to the class 
of compound racemose glands, and closely re- 
sembles the salivary glands, though of some- 
what looser texture, the lobules being separated 
by more connective tissue. 

Pancreatic Juice is a clear, viscid alkaline 
fluid resembling saliva, but of greater specific 
gravity, and containing about 2 per cent, of 
solid matter. About 12-16 oz. are secreted in 
24 hours. 



MEMORANDA OF PHYSIOLOGY. 



167 



It contains- 



1. Four ferments. 

(a) Trypsin, changes proteids into 

peptones. 
(5) Pancreatic diastase, changes 

starch into dextrin and sugar. 

(c) Curdling ferment, curdles the 

casein of milk. 

(d) Emulsive ferment, emulsifies and 

saponifies fats. 

2. Albumen. 

3. Mucin. 

4. Salts and 



Action. 

.1. It changes proteids into peptones in al- 
kaline or neutral solutions, afterward decom- 
posing them into leucine and tyrosine. 

2. It converts starch into dextrin and sugar. 

3. It emulsifies and saponifies fafcs. 

On Proteids. — Pancreatic juice artificially 
prepared from pancreas acts in a somewhat 
similar manner on proteids as gastric juice, 
more leucine and tyrosine however are formed* 
It acts energetically on some proteids, as the 
casein of milk, provided the solution is alkaline, 



168 MEMOBAISTDA OF PHYSIOLOGY. 

but acts less actively than artificial gastric en 
white of egg. Its solutions require to be alka- 
line, equivalent to one per cent, of sodium car- 
bonate. Its activity depends upon a ferment 
called trypsin. 

Pancreatic digestion of proteids differs from 
gns^ric, in that, 1, it requires an alkaline instead 
of acid medium ; 2, the proteids are dissolved 
without the preliminary swelling ; 3, leucin and 
tyrosin are formed. 

On Starch. — Pancreatic juice acts with great 
energy on cooked starch, quickly converting it 
into dextrin and sugar. 

On Fats. — Pancreatic juice when shaken up 
with fats and oils, reduces the oily matters to a 
state of fine division and suspends them, form- 
ing a milky fluid. 

An artificial pancreatic juice can be made by 
pounding up fresh pig's pancreas with powdered 
glass, and adding dilute spirit or glycerine. 

Succus Enteric us. — This is the secretion of 
the intestinal glands. It appears to act in a 
similar way to pancreatic juice. It also con- 
tains a ferment which converts cane sugar into 
invert sugar. 



MEMOKANDA OF PHYSIOLOGY. 169 

THE LARGE INTESTINE. 

The large intestine consists of caecum, colon, 
rectum. 

Structure — resembles the small intestine, with 
some modifications. 

The Serous coat completely surrounds the 
intestine in the transverse colon ; is incomplete 
elsewhere. 

The Muscular coat consists of two layers, 
the longitudinal being arranged in three flat 
bands, except at the rectum. One band is pos- 
terior, another anterior, and a third lateral or 
inferior in the transverse colon ; along the lat- 
ter the appendices epiploicas are attached. 
These longitudinal fibres, by being shorter 
than the intestine, throw it into sacculi, which 
are marked off from one another by constric- 
tions where the circular fibres are most marked. 
The circular fibres form a thin layer over the 
intestine, and are best marked at the constric- 
tions. 

The Mucous membrane is lined with col- 
umnar epithelium, and is destitute of villi. It 
has numerous glands of Lieberkuhn and solitary 
glands, also retif orm tissue. 

The junction of the small and large intestine 
is guarded by a valve, and the termination of 



170 MEMOEANDA OF PHYSIOLOGY. 

the rectum by the sphincter. But little, if any, 
digestive action goes on in the large intestine ; 
the principal work done is absorption; the con- 
tents of the intestine become firmer and harder 
as they approach the rectum. The contents of 
the large intestines are acid, from the acid fer- 
' mentations going on in the fecal matters. 

Movements of the Intestines. 

If the abdomen of a recently killed animal be 
opened, the muscular fibres of the intestine will 
be seen alternately contracting and relaxing, but 
working down the intestine in waves so as to 
propel the contents downward. This peristal- 
tic action is increased by the presence of food 
or bile, or by irritation of the vagus nerve. It 
is checked by irritation of the splanchnic. The 
exact nervous mechanism is unknown, but it is 
probably automatic like the action of the heart. 
The movements of the large intestine resemble 
those of the small ; the faeces are lodged in the 
sacculi during the relaxation of the intestine. 

Defecation. — The sphincter is normally con- 
tracted under the influence of a nervous centre 
in the cord. The sigmoid flexure prevents the 
faeces from pressing too heavily on the rectum. 
The act of defecation consists in an inhibition 



MEMORANDA OF PHYSIOLOGY. 171 

of the nervous centre in the cord which governs 
the sphincter, relaxation of the sphincter taking 
place. At the same time a deep breath is taken, 
the glottis is closed, the diaphragm and abdomi- 
nal muscles contract, press upon the descending 
colon, and eject the contents of the rectum, the 
sigmoid flexure having previously become filled 
by peristaltic action. 

Summary of Digestive Changes. 

The essential work of digestion is performed 
by a singular group of bodies termed ferments. 
These bodies are found in nearly all the secre- 
tions poured into the alimentary canal, and play 
an exceedingly important part in dissolving the 
food. These ferments are soluble in water, and 
differ in this respect from the organized insol- 
uble forms as the yeast plant. They diffuse 
through animal membranes, though with diffi- 
culty ; they are rendered inert by a heat of 70° 
C. (160° F.), and they are precipitated by strong 
alcohol. 

The Mouth.— The food is crushed, mixed 
with saliva, and reduced to a pulp; a certain 
amount of starch converted into maltose and 
rendered slightly alkaline. Fats and proteids 
unaltered. 



172 



MEMOBANDA OF PHYSIOLOGY. 



Table of the Digestive Juices and Their Fer- 
ments (Roberts). 



Digestive Fluid. 


Ferments. 


Action. 


Saliva 


Ptyalin or 
Diastase. 


Changes starch into dex- 




trin and sugar. 


Gastric juice.. 


(a. Pepsin, 

i 

i 

| b. Curdling 
[ ferment. 


Changes proteids into 
peptones in an acid 
solution. 

Curdles casein of milk. 


Pancreatic juice. 


fa. Trypsin. 

1 6. Curdling 
ferment, 

c. Diastase. 

d. Emulsive 
ferment. 


Changes proteids into 

peptones in alkaline 

solutions. 
Curdles the casein of 

milk. 
Changes starch into 

sugar. 
Emulsifies and partly 

saponifies fats. 


Intestinal juice. . 


Invertin. 


Changes cane-sugar into 
invert-sugar. 



The Stomach. — Contents rendered acid, con- 
version of starch into sugar ceases, connective 
tissue of fats dissolved, and fats set free. 
Proteids dissolved and peptones formed. The 



MEMORANDA OF PHYSIOLOGY. 173 

albuminous foods are dissolved for the most 
part, and a grumous mixture of peptones, liquid 
fats, and starches is formed, which is termed 
chyme, and is gradually passed through the 
pylorus into the intestine. 

In the Intestine. — The chyme mixes with the 
bile, pancreatic, and intestinal juices, becomes 
alkaline, conversion of starch into sugar re- 
commences, emulsifying of fat begins, and the 
undissolved proteids are converted into pep- 
tones. The diffusible peptones and salts enter 
the portal vein, the fat in a fine state of division 
entering the lacteals. In the large intestine the 
liquid chyme becomes more and more solid, is 
rendered acid by fermentative changes, and ac- 
quires the odor of faeces. 



©ectton 10. 
ABSOKPTION AND NUTKITION. 

The food must be acted upon by the various 
secretions of the alimentary canal before it can 
enter the blood-vessels or lacteals with which 
the walls of the stomach and intestines are well 
supplied. 

The Albuminous Foods are crushed and re- 
duced to pulp in the mouth, and converted into 
the peptones by the action of the gastric, pan- 
creatic, and intestinal juices. By far the 
greater part of the peptones thus formed enter 
the capillary blood-vessels of the stomach and 
villi. Being diffusible through animal mem- 
branes, they pass through the walls of the cap- 
illaries by osmosis, enter the portal vein, and 
are conveyed to the liver. In the liver they 
are either split up into more oxidized bodies, as 
glycogen, urea, or kreatin, or are reconverted 
into albumen to assist in the nutrition of the 
tissues. 

The Starches are converted into dextrin and 



MEMOBANDA OF PHYSIOLOGY. 175 

sugar by the action of the saliva, pancreatic, 
and intestinal juices, and being thus rendered 
diffusible enter the portal vein, and are conveyed 
to the liver. The liver probably converts the 
sugar into glycogen, and stores it up till re- 
quired to be oxidized for the production of heat 
and muscular energy. « 

The Fats are crushed and reduced to pulp in 
the mouth, and their fibrous tissue and vesicu- 
lar envelopes dissolved in the stomach, so that 
the oily matters are set free. In the small in- 
testine they undergo two different changes, 
which are effected by the secretions of the small 
intestine — 

1. They are emulsified. 

2. They are saponified. 

The emulsification consists in reducing the 
fat into fine particles, small enough to readily 
enter the lacteals. The saponification consists 
in the formation of soaps : thus olein is de- 
composed, the glycerine being set free, and the 
oleic acid forming an oleate with sodium or 
potassium for a base. 

Small quantities of the fatty matters find 
their way into the portal vein, but by far the 
major quantity enters the lacteals of the villi. 
The particles of fat enter the protoplasm of the 



176 MEMORANDA OF PHYSIOLOGY. 

columnar cells surrounding the villi, so that if 
these cells be examined during a period of di- 
gestion, they are seen to be distended with fat 
particles. They next pass into the retiform 
tissue of the villi, and thence into the lacteal, 
which commences in the villus. Finally, the 
fatty matters forming the chyle pass through 
the mesenteric glands and into the receptaculum 
chyli and thoracic duct. 

The exact forces in operation which deter- 
mine the entrance of fat into the lacteals are 
not thoroughly understood. Animal membranes 
wetted with bile much more readily allow 
fatty matters to pass through them than mem- 
branes not so treated. The cells surrounding 
the villi, perhaps, exercise some selective power, 
as the glandular epithelium does in the con- 
voluted tubes of the kidney. The fat once 
within a villus is driven onward by the con- 
traction of the muscular fibre present in the 
villi, compressing the lacteal and forcing on- 
ward its contents ; the aspirating power of the 
thorax supplying the vis a fronte. The fatty 
matters and albuminous materials present in 
the chyle are gradually, in part, converted dur- 
ing its passage through the mesenteric glands 
into the elements of fibrin and white blood-cor- 
puscles. 



MEMORANDA OF PHYSIOLOGY. 177 

The food that has entered the body in the 
form of meat, starch, sugar, fats, after being 
digested passes into the blood-yessels in the 
form of peptones, fatty matters, and sugar. 
What processes must they undergo before they 
become formed tissue, such as muscle, nerve, 
tissue, or gland ? But very little is known of 
such changes. Some of the albuminous and 
fatty matters are converted into white corpus- 
cles and fibrin, probably through the action of 
the blood-glands, i. e. , spleen, lymphatic, lentic- 
ular, tonsils, thymus glands ; the white cor- 
puscles passing into red or exuding into the 
tissues to become transformed into the actual 
cells or fibres of the various tissues. 

The albumen, fats, and sugars absorbed from 
the alimentary canal, pass out of the body at 
the kidneys and lungs as urea, salts, and C0 2 . 
About the intermediate stages our knowledge is 
scanty. 

Summary. 

r Peptones (major part) 



The portal vein 
absorbs 



12 



Sugar " 

Salt " 

Soaps " 

Fats (trace) 

Water (major part) 



A 



178 



MEMOEANDA OF PHYSIOLOGY. 



The lacteals 
absorb 



Fats (major part) 

Soaps (small part) 

Peptones u 

Sugar (trace) 

Salts 

Water (small part) 



IC 



Section 11. 
THE LIVER 

The liver is the largest gland in the body, and 
weighs 50 to 60 ozs. In the foetus and child it 
is larger in proportion to the body- weight than 
in the adult, being 1 in 20 to 80 in the child and 
1 in 40 in the adult. The liver receives the 
blood of the portal vein and hepatic artery, the 
hepatic veins carrying away the blood from 
the organ. Its under surface is divided into 
lobes by five fissures. 

The Fissures are the transverse where the 
vessels and nerves enter ; the longitudinal, sit- 
uated btween the right and left lobes, is divided 
into two by the transverse fissure, the anterior 
part forming the umbilical fissure and contain- 
ing the round ligament, and the posterior the 
fissure of the ductus venosus, containing the ob- 
literated remains of the ductus venosus of the 
foetus. The fissure of the gall-bladder, or rather 
fossa, makes the fifth. 



180 MEMORANDA OF PHYSIOLOGY. 

The Lobes are, right and left, separated by 
the longitudinal fissure. The lobulus quadratus 
situated between the gall-bladder and longi- 
tudinal fissure. The lobulus Spigelii between j 
the fissure for the ductus venosus and inf. vena 
cava. The lobulus caudatus forms a sort of. 
ridge extending from the base of the Spigelian 
lobe to the under surface of the right lobe. 

Structure. — The liver has two coverings, the 
serous and fibrous coats. 

The Serous is derived from the peritoneum, 
and is reflected round the organ, except where 
the vessels enter, and at the posterior border. 

The Fibrous or Connective Tissue coat in- 
vests the whole gland, and at the transverse fis- 
sure becomes continuous with the fibrous tissue 
which accompanies the blood-vessels into the 
substance of the liver and forms the capsule of 
Glisson. 

Hepatic Lobules. — On section of the liver 
its substance will be seen to be composed of 
closely packed bodies of rounded outline and of 
about -fa to -gV in. in diameter. These lobules 
for the most part have a darkish red centre and 
lighter circumference, and in some animals, at 
least, are separated by a small quantity of con- 
nective tissue. The centre of the lobule is oc- 
cupied by an intralobular vein, which collects 



MEMORANDA OF PHYSIOLOGY. 181 

the blood from the capillaries of the lobule and 
empties itself into the sublobular ; the latter 
opens into the hepatic veins. The circumfer- 
ence of the lobule is surrounded by the inter- 
lobular veins, which are branches of the portal 
system ; capillaries passing from the circumfer- 
. ence to the centre of the lobule connect the in- 
terlobular veins with the intralobular. 

The Hepatic Artery enters the liver at the 
transverse fissure, accompanies the portal vein 
and ducts, and supplies the connective tissue 
of the liver. 

The Hepatic Cells are packed in between the 
network of capillaries in the lobule. They are 
of rounded or polyhedral form, •&$ to toott m - m 
diameter. They have a yellow granular appear- 
ance and a well-marked prominent nucleus. 
They contain minute oil-globules and glycogen. 

The Biliary Ducts commence by a fine plexus 
of capillaries which run between and surround 
the cells. In a very thin section minute open- 
ings may be seen between the cells, which are 
the apertures of the capillary ducts. The 
larger bile-ducts are lined with columnar epi- 
thelium, their coats being formed of fibrous and 
elastic tissue with a mixture of unstriated mus- 
cular fibre. 

The branches of the portal vein, artery, and 



182 MEMORANDA OF PHYSIOLOGY. 

duct accompany one another through the liver, 
the hepatic veins travelling by themselves, 

FUNCTIONS OF THE LIVER. 

The portal vein carries the blood which has 
circulated through the walls of the stomach and ■ 
intestines, pancreas, and spleen. It is loaded 
with material absorbed from the contents of the 
stomach and intestines. This blood is submitted 
to the liver before entering the general circula- 
tion. In its circulation through the liver it 
enters the interlobular plexus, travels through 
the capillaries of the lobule, coming into close 
relation with the hepatic cells, enters the intra- 
lobular veins, and finally the hepatic veins con- 
vey it to the inferior vena cava. 

The liver in the adult has at least three func- 
tions — 

1. Formation of glycogen. 

2. Action on albuminous substances. 

3. Secretion of bile. 

4. In the foetus it appears to give origin to 
white blood-corpuscles. 

1. Glycogen or Amyloid Substance (C 6 Hi 
5 ), is present in the cells of the healthy liver. 
When pure it is a white, tasteless, inodorous 
powder, insoluble in alcohol, soluble in water, 



MEMORANDA OF PHYSIOLOGY. 



183 



forming a white opalescent solution. It closely 
resembles starch in appearance, but differs from 
it in being stained reddish-brown by iodine. 
Like starch it is readily converted into grape- 
sugar by the action of dilute acids or ferments. 
Besides being present in the liver it is found in 
living muscle, white corpuscles of the blood, 
brain, placenta, and most tissues of the foetus. 

Preparation.— Fresh liver is boiled with 
strong solution of KHO, which dissolves the 
liver-tissue and the glycogen, and on pouring it 
into alcohol the glycogen is precipitated toler- 
ably pure. Another method consists in making 
a decoction of liver, precipitating the albumi- 
nous matters with potassic hydrarg. iodide and 
HC1, and afterward precipitating the glycogen 
with alcohol {see p. 11). 

Origin. — Glycogen is principally formed in 
the liver from the saccharine elements of the 
food. 

C6H12O6 — H2O = CeHioOs. 
Grape-sugar — water = glycogen. 

Dogs fed on starch or sugar rapidly accumu- 
late large quantities of glycogen in the liver ; 
when fed on a purely animal diet very much 
smaller quantities are found. This appears to 
show that while glycogen is formed in small 



j 



184 MEMORANDA OF PHYSIOLOGY. 

quantities from albumen, yet by far the major 
part originates fiom the saccharine elements of 
the food. 

Destiny of Glycogen.— The fate of glycogen 
is uncertain. There can be no doubt it serves 
to store up material rich in C and H ; but the 
exact manner in which it is utilized is not fully 
understood. Bernard maintained that it is 
gradually reconverted into sugar as required, 
and oxidized in the capillaries of the body to 
maintain the heat or to supply muscular energy. 
He based this view on his analysis of the blood, 
which showed that a larger quantity of sugar 
existed in the hepatic than in the portal vein. 
He also found a greater quantity in the arteries 
than in the veins, which seemed to suggest that 
sugar disappeared in the capillaries. Pavy 
maintains that the hepatic veins during life 
only contain a trace of sugar, and the arteries 
contain no more than the veins. He argues 
that the large quantities of sugar found in the 
hepatic veins after death are due to a post- 
mortem change of glycogen into sugar, and that 
during life only traces are to be found. He 
does not believe that glycogen is reconverted 
into sugar during life, and that if it were in any 
quantity, it would run off at the kidneys as in 
diabetes. The question is still subjudice* Gly- 



MEMORANDA OF PHYSIOLOGY. 185 

cogen is doubtless stored in the liver and is 
utilized in the system, either entering the blood 
as sugar or as glycogen in the white corpuscles, 
or in some other way. That it cannot enter 
the blood as sugar in any large quantity is» cer- 
tain, as, if it did, it would certainly be excreted 
in the urine as in diabetes. Bernard found 1 
grm. per 1,000 in the arteries, and 3-7 grms. 
per 1,000 in the hepatic veins. This quantity 
seems too small to be of any great use in main- 
taining the energy of the body, and not im- 
probably the glycogen may be utilized in some 
other way. ■ 

Diabetes is a disease characterized by the 
persistent presence of sugar in the urine. Its 
immediate cause is a rapid conversion of glyco- 
gen into sugar in the liver, depending probably 
on some disturbed innervation of the blood-ves • 
sels. It can be induced artificially in animals 
by puncture with a needle of the vaso-motor 
centre of the medulla. This leads to dilatation 
of the blood-vessels of the liver, an increased 
supply of arterial blood, and an increased con- 
version of glycogen into sugar, which makes its 
appearance in the urine. 

2. Action on Albuminous Substances. — (a) 
Preparation of the peptones for assimilation. 
(b) Splitting up of various bodies into urea, etc, 



186 MEMOBANDA OF PHYSIOLOGY. 

(a) The portal vein contains the peptones 
which have been absorbed from the alimentary- 
canal. These bodies disappear during their 
passage through the liver, being probably con- 
verted into serum albumen. 

(b) The liver probably splits up various sub- 
stances, as albumen, kreatin, leucin, and tyro- 
sin, the products being glycogen, urea, and uric 
acid. In certain diseases, as acute yellow 
atrophy of the liver, the urea in the urine is 
lessened, and tyrosin and leucin appear to take 
its place. 

3. Secretion of Bile. — In all probability the 
pigments and biliary acids are formed in the 
liver and not merely separated from the blood. 
No trace of either of them has been found in 
frogs whose livers have been extirpated. To 
what extent the secretion of bile gets rid of 
effete matters from the system is uncertain. 
The biliary acids are in large part reabsorbed 
after having taken part in the digestion of the 
contents of the small intestine. 

4. Foetus. — The relative size of the liver in 
early fetal life is about half the body weight ; 
at full time it is about 1 in 18. It receives 
blood from two sources — {a) the umbilical vein, 
a portion of which escapes through the duc- 
tus venosus directly into the inf. vena cava ; (b) 



MEMORANDA OF PHYSIOLOGY. 



187 



the portal vein, which carries venous blood re- 
sembling that of the body generally. The 
functions of the fetal liver differ from those of 
the adult, principally in its being a blood-mak- 
ing organ. After the formation of the placenta 
the umbilical vein brings various nutritive ma- 
terials from the maternal system ; the liver 
seems out of these materials to produce numer- 
ous colorless nucleated corpuscles which are 
poured into the blood. Probably before birth it 
ceases to do so, the spleen and lymphatic glands 
taking its place. 

The biliary secretion (meconium) of the foetus 
is purely excrementory in character. 



Section 12, 

THE KIDNEYS. 

The kidneys are situated in the lumbar re- 
gion opposite the last dorsal and two or three 
upper lumbar vertebrae. They are about four 
inches in length and weigh four to five ounces 
each. 

Structure. — On making a longitudinal section 
through a kidney the glandular structure will 
appear to be divided into two portions, (1) the 
outer or cortical portion, for the most part oc- 
cupying the surface, except atthehilus ; (2) the 
medullary portion, consisting of a number of 
pyramids separated from one another by corti- 
cal substance. 

1. The Cortical Substance occupies the 
greater part of the gland, being one- third to one- 
half inch in depth at the surface, and extends 
into the centre of the gland between the pyra- 
mids. The cortical portion between the pyra- 
mids being termed the columns of Bertini. It 



MEMOBANDA Otf PHYSIOLOGY. 189 

is of a light red color, and with the aid of a 
lens is seen to be studded over with bright red 
points, the Malpighian bodies. Besides these 
bodies, it contains convoluted tubes, the com- 
mencement of the collecting tubes, blood-vessels, 
lymphatics, and nerves. 

The Medullary Portion occupies the centre 
of the gland, and consists of 8-12 of the pyra- 
mids of Malpighi. These pyramids are sur- 
rounded at their bases and sides by cortical sub- 
stance, while their apices project into the 
dilated portion of the ureter at the hilus, 
which forms the pelvis. They are of a purplish 
color .and marked with longitudinal striae, and 
contain collecting tubes, looped tubes of Henle, 
blood-vessels, and nerves. 

Urinary Tubules. — The Malpighian bodies are 
T ^o in. in diameter, scattered through the cor- 
tical substance of the kidney. They consist of 
a tuft of capillary vessels contained in a capsule 
formed by the dilated end of a urinary tubule, 
called the Malpighian capsule. The tuft of cap- 
illary vessels receives an arterial twig from an 
interlobular artery, and its efferent vessel forms 
a plexus surrounding the corresponding convo- 
luted tube -before joining an interlobular vein. 
The Malpighian capsule is formed of homogen- 
eous membrane, lined by flattened epithelium, 



190 MEMOBANDA OF PHYSIOLOGY. 

and joins a convoluted tube by a constricted 
neck. 

The Convoluted Tubes commence as cap- 
sules in the cortex, twist upon themselves sev- 
eral times, and then descend in the medullary 
portion as a looped tube of Henle. They are 
lined by epithelium of a cubical or spheroidal 
shape, leaving a very small lumen in the centre, 
and are surrounded by a capillary plexus. 

The Looped Tubes of Henle, commencing 
at the termination of the convoluted tubes, de- 
scend for some distance, bend suddenly round 
and re- ascend again, the ascending and de- 
scending portions being parallel ; they termi- 
nate in a portion of tube which is again con- 
voluted. The looped tubes are narrower in 
calibre than the convoluted, and are lined by 
flattened epithelium. The second convoluted 
tube resembles the first portion, and empties 
itself into a collecting tube. 

The Collecting Tubes are straight, and pass 
in bundles from the base of a pyramid to its 
apex. They are wider than the looped tubes, 
receive numerous other tubes, and are lined 
with columnar epithelium. A cut section of a 
pyramid shows numerous large apertures lined 
with columnar epithelium, the collecting tubes, 
— many small ones lined with flattened epi- 



MEMORANDA OF PHYSIOLOGY. 191 

thelium — the looped tubules of Henle, and the 
cut section of blood-vessels, the vasa recta. 

Pyramids of Perrein — This term is applied 
in two senses, either to the portion of gland oc- 
cupied by all the convoluted tubes which join 
one collecting tube, or to the bundles of col- 
lecting tubes seen in the cortical portion prior 
to their entrance into a pyramid. 

Blood-Vessels. — The renal artery, on enter- 
ing the kidney, breaks up into numerous pri- 
mary branches, which travel along the columns 
of Bertini, and are called the arterim proprim 
renales. 

These divide at the base .of the pyramids and 
form arches with their neighbors ; these arches 
give off (1) branches into the cortex termed the 
interlobular arteries, from which the afferent 
vessels to the Malpighian tuft arise ; (2) 
branches downward into the pyramids running 
between the bundles of collecting tubes and 

termed the vasa recta or arterim reetce. 

» 

The Renal Veins. — The venm interlobulares 
correspond with the arteries and receive some 
veins termed stellate from beneath the capsule, 
and also the small veins which receive the 
blood from the minute plexus surrounding the 
convoluted tubes. 



192 MEMORANDA OF PHYSIOLOGY. 

The vena recta run along the pyramids accom- 
panying the corresponding arteries. 

The vena propria renales pass along the col- 
umns of Bertini after having been joined by the 
venaa interlobulares and venaa rectae. 

The Lymphatics occupy the meshes of the 
connective tissue which exists immediately un- 
der the capsule of the organ, pass between the 
uriniferous tubes and around Bowman's capsule 
and finer blood-vessels toward the deeper por- 
tions of the kidney. 

The Nerves belong to the sympathetic sys- 
tem, but their course and termination are un- 
known. 

Pelvis and Ureter. — The ureters convey the 
urine to the bladder, their upper dilated portion 
forming the pelvis. The pelvis is divided into 
two or three primary divisions, and these again 
divide into shorter ones termed calices or in- 
fundibida, which receive the papillae or apices 
of the pyramids of Malpighi. The collecting 
tubes open at the papillas and discharge .their 
contents into the pelvis. The pelves and 
ureters are lined by transitional epithelium 
— layers of cells flattened, rounded, and cau- 
date. 



MEMOKANDA OF PHYSIOLOGY. 



193 



URINE. 

The urine is a clear yellow fluid of specific 
gravity 1020, of peculiar odor and acid reaction. 
It is constantly being secreted by the kidneys, 
and is collected in the bladder. On an average 
52 ozs. (1,500 c.c.) are passed per diem. The 
solids amount to about 4 per cent. The princi- 
pal constituents are the following, with their 
amounts, in 24 hours : — 



Urea, 

Uric acid, 7 — 8 

Kreatinin, 14 

Hippuric acid, 6 

Chlorides, 105 

Sulphates, 

Phosphates, 

Sodium, 

Potassium, 

Ammonia, 

Earthy 'salts, 

Pigment, etc. 



500 gr. or 33 grammes, 2.2 per c. 



.5 
.9 

.4 

.7 



► Smaller quantities. 



.3 



Sources of Urea — The greater part of the 

effete nitrogen of the body passes out of the 

system in the form of urea, a much smaller 

quantity in the uric acid, kreatinin, hippuric 

13 



194 MEMOEANDA OF PHYSIOLOGY. 

acid, and other minor constituents. The stages 
by which the albumens and peptones are con- 
verted into urea are ill understood. It is not, 
indeed, certain whether the urea is simply ex- 
creted from the blood by the kidneys, or whether 
the epithelium of the convoluted tubes does not 
convert the kreatin present in the blood into 
urea, to be thrown off into the urine. The two 
most probable sources of urea are : 

(1) From kreatin. 

(2) From leucin and tyrosin. 

(1.) Kreatin is found in the blood, and in 
most of the tissues of the body. Muscle con- 
tains from .2 to .4 per cent., while urea does not 
exist in muscle, and only to a very small extent, 
if at all, in the various organs. It is possible 
that kreatin represents the waste product of the 
albumen of the tissues. That in consequence 
of the changes necessitated by life there is a 
constant formation of kreatin in all the tissues 
of the body, and that this kreatin passes into 
urea in the liver or in the kidneys. The small 
increase of urea in the urine after active exertion 
would, on this view, represent an increased wear 
and tear, leading to an increased formation of 
kreatin and urea. 



MEMORANDA OF PHYSIOLOGY. 195 

(2. ) If the amount of nitrogenous food be in- 
creased in quantity, the amount of urea excreted 
in the urine is also increased. This would 
indicate that a certain part of the albumen of 
the food is split up into urea, etc., without its 
having taken part in the formation of any 
tissue. Leucin and tyrosin are found in the 
small intestine, and are formed when pancreatic 
juice acts upon albuminous foods. It is proba- 
ble that the leucin and tyrosin enter the portal 
veins, and are converted into urea in the liver. 
This is rendered the more probable from the 
fact already mentioned, that in acute yellow 
atrophy of the liver, leucin and tyrosin replace 
urea in the urine. 

Amount of Urea. — About 500 grains of urea 
escape at the kidneys during 24 hours, but this 
amount varies according to circumstances. The 
amount being increased after large quantities of 
animal food, slightly after exercise, and also 
during fevers. The urea is diminished after 
vegetable food or fasting, and in certain forms 
of kidney disease. 

Uraemia. — In certain conditions of the body, 
such as Bright's disease and in fevers, there is 
a greater accumulation of effete material in the 
body than can be carried off by the kidneys. 
Certain toxic effects, such as convulsions and 



196 MEMOKANDA OF PHYSIOLOGY. 

coma, result. This is probably, though not cer- 
tainly, due to the accumulation of kreatin in 
ths blood. 

Estimation of Urea.— There are two meth- 
ods. (1) Liebig's ; (2) Russell and West's. 

(1.) Liebig's method depends upon the fact 
that urea forms an insoluble precipitate with 
mercuric nitrate. Before the estimation can 
be made, the sulphates and phosphates present 
are precipitated by baryta water, and the liquor 
filtered. A certain quantity of the filtrate is 
taken, and a solution of mercuric nitrate of 
known strength (10 c.c. =.1 grm. of urea) is 
dropped into the urine with frequent agitation : 
a white precipitate falls. From time to time 
as the mercuric solution is added, a drop of the 
liquid is tested' on a white slab with a drop of 
solution of sodic carbonate, when all the urea 
is precipitated and free mercuric nitrate present 
in the solution ; a yellow precipitate occurs with 
the sodic carbonate. The amount of mercuric 
solution added is read off, and the corresponding 
amount of urea estimated. If great accuracy 
is required, the amount of CI present must be 
estimated, and an allowance made in estimating 
the urea, as no precipitate of urea occurs until 
all the chlorine present has combined with the 
mercury. 



MEMOKANDA OF PHYSIOLOGY. 197 

(2 ) Russell and West's method depends upon 
the fact that urea is decomposed by hypobro- 
mous a'cid, into C0 3 , N, H 2 0. The C0 2 is ab- 
sorbed in passing through a solution of NaHO 
and the N measured in a graduated tube. The 
amount of N given off indicates the amount of 
urea present in the urine. 

Uric Acid. — Some 7 to 8 grs. of uric acid are 
excreted daily in the urine, for the most part 
in the form of urates of potassium, sodium, or 
ammonium. The amount varies, being in- 
creased after animal diet, and in certain diseases, 
as gout. Its source is uncertain, being like urea 
a waste product formed from the breaking up 
of nitrogenous compounds. It is probable that 
in certain derangements of the liver, uric acid 
is formed instead of urea. It represents a less 
oxidized form than urea. 

Kreatinin. — Some 14 grains daily of kreatinin 
escape by the kidneys. Probably the greater 
portion of kreatin formed in the body has been 
converted into urea, a small amount being con- 
verted into the kreatinin which escapes with the 
urine. 

Hippuric Acid. — Only about 6 grs. of hip- 
puric acid are secreted daily in man ; though a 
very much larger amount is present in the urine 
of the herbivora. 



198 MEMOKANDA OF PHYSIOLOGY. 

Pigments.— The yellow color of the urine is 
due to several pigments, the nature of which is 
ill understood. Indican also occurs in the urine 
in variable quantities ; it is known by the pres- 
ence of a blue color due to the formation of 
indigo, when strong acids are Ridded to the 
urine. 

Inorganic Salts. — These are numerous, the 
most abundant being sodium chloride, smaller 
quantities of potassium, magnesium, calcium in 
the form of phosphates, sulphates, chlorides, 
and carbonates. The amount and variety of 
the salts in the urine differ according to the 
food taken : the alkalies being increased dur- 
ing a vegetable diet, the urine becoming alka- 
line, the earthy salts being increased when 
animal food is taken. 

Secretion of Urine. 

The Malpighian bodies, and that portion of 
the urinary tubules known as the convoluted 
tubes, are both engaged in the separation of the 
urine from the blood. The Malpighian bodies, 
as before explained, consist of a tuft of capil- 
laries fitting inside a capsule communicating 
with the convoluted tubes, and are probably 
engaged in secreting the greater part of the 



MEMORANDA OF PHYSIOLOGY. 199 

water and inorganic salts of the urine, the pro- 
cess consisting in a simple transudation depend- 
ing upon the pressure in the capillary tuft. 

The convoluted tubes are lined by glandular 
epithelium and are surrounded by a plexus of 
capillaries. The epithelium lining thern ap- 
pears to exercise a certain selective influence in 
secreting the urea and uric acid and pigment, 
or possibly actually effects the change of kreatin 
into urea. These substances, having been sepa- 
rated from the blood and entered the urinary 
tubules, are washed down by the water and sa- 
lines transuding through the capillary tufts into 
the capsule above. 

The amount and character of the urine largely 
depends upon the blood-pressure in the capil- 
laries of the kidney. If the pressure be in- 
creased larger quantities of water will be passed, 
and under certain circumstances, as in nephri- 
tis, albumen, blood, and fibrinous material. 
The blood-pressure will depend upon the vaso- 
motor nerves distributed to the renal arteries, 
also on the state of the general circulation, as 
well as on the action of the heart. Section of 
the renal nerves causes dilatation of the renal 
arteries, increase of capillary pressure, and an 
increased secretion of the watery constituents 
of the urine. 



200 MEMOKANDA OF PHYSIOLOGY. 

Section of the spinal cord below the medulla, 
causes a general dilatation of the blood-vessels 
throughout the system, and consequent lower - 
iag of the blood-pressure in the renal arteries, 
and almost complete arrest of the secretion of 
urine. 

Stimulation of the divided cord below the 
medulla produces a similar result, though not 
so marked, by causing general constriction of 
the arteries, including the renal, the increased 
tension in the general arteries not being suffi- 
cient to overcome the resistance offered by the 
constricted renals. 



0wtton 13. 

THE DUCTLESS GLANDS. 

The spleen, lymphatic glands (including lenticu- 
lar glands of alimentary canal and tonsils), su- 
pra-renals, thymus and thyroid, form the 
ductless glands. The pituitary , pineal, and 
coccygeal bodies are not in any sense glands, nor 
have they probably any analogous function to 
them. 

SPLEEN. 

TnE spleen is the largest and most important 
of the ductless glands. It is a soft, red, vascu- 
lar organ, situated at the cardiac end of the 
stomach beneath the diaphragm. It has two 
coats, a serous and fibro- elastic. 

The Serous closely invests its surface, except 
at the hilus and at the spot where it is reflected 
to the stomach and diaphragm. 

The Fibro- elastic or Tunica propria is a 
strong capsule surrounding the organ, and pass- 



202 MEMOEANDA OF PHYSIOLOGY. 

ing into its substance at the hilus forms a 
sheath for the vessels and trabecule, which 
divide the gland into spaces occupied by the 
pulp. It consists of white and yellow fibrous 
tissue, and non-striated muscular- fibre, the lat- 
ter well marked in the pig and dog, but more 
scanty in man. The capsule is highly elastic, 
and capable of great distention. 

The Spleen Pulp occupies the spaces between 
the trabeculae, is of a dark red color, and semi- 
solid consistence. The pulp, when examined 
in thin sections beneath the microscope, is 
seen to consist of a network of branched con- 
nective-tissue corpuscles, the branches joining 
one another, and forming a fine retiform tissue. 
Many of these connective-tissue corpuscles con- 
tain a clear oval nucleus, and some contain yel- 
lowish pigment granules, possibly derived from 
the blood-corpuscles. The spaces between these 
branched cells contain red and white blood- cor- 
puscles, the white being in larger proportion 
than in ordinary blood. 

The Splenic Artery enters the spleen by 
dividing into six or more branches, which ram- 
ify in the interior, supported by the trabecule, 
and break up in the pulp into fine branches. 
The small arteries terminate in capillaries, the 
walls of which eventually are lost, their cells 



MEMORANDA OF PHYSIOLOGY. 203 

becoming gradually transformed into the con- 
nective-tissue corpuscles of the pulp, and their 
contained blood wanders freely through the 
retiform tissue of the pulp. The minute veins 
arise in a manner similar to that in which the 
arteries terminate, and eventually empty them- 
selves into the splenic vein. Thus the blood, in 
its course through the spleen after leaving the 
arteries, wanders freely through the pulp before 
entering the veins. 

The Malpighian Corpuscles are small bod- 
ies, about -g^o in. in diameter, and may readily 
be seen in the child's spleen as small white dots 
scattered thickly over the cut surface. They 
are seated upon the small arteries, their sheath 
being continuous with that of the arteries, 
though in man the sheath is not very distinct, 
and the tissue of the Malpighian body is con- 
tinuous with that of the spleen pulp. In struc- 
ture they consist of lymphoid tissue, the 
leucocytes being densely packed in a fine net- 
work. A small artery enters their substance. 

Functions. — The exact functions performed 
by the splee^n in the animal economy are ill- 
understood; the most certain are the follow- 
ing: 

(1.) During digestion the spleen becomes 
congested, the arteries and trabecule being 



204 MEMORANDA OF PHYSIOLOGY. 

relaxed, the elastic tissue yielding, and the 
organ containing more blood. This has been 
attributed by some to the necessity of having 
an excessive quantity of blood in the portal 
system during digestion, the spleen acting as a 
reservoir, but more probably it is connected 
with important changes going on in the spleen 
pulp. 

(2.) The spleen is a source of white blood- 
corpuscles to the blood ; the splenic vein con- 
taining 1 white to 60 red, whereas in ordinary 
blood it is 1 to 400. The blood in passing 
through tho pulp comes into close relation wifch 
the lymphoid tissue, and new corpuscles are 
formed. 

(3.) Red corpuscles are probably broken up 
and disintegrated in the spleen. The spleen 
pulp shows yellowish granular matter, which 
may be derived from the hsemoglobin of the red 
corpuscles. This coloring matter may be con- 
verted into pigment in the liver. 

(4.) The conversion of white corpuscles into 
red has been attributed to the spleen, but this 
is very uncertain. 

LYMPHATIC GLANDS 
Have already been referred to (p. 94.) 



MEMORANDA OF PHYSIOLOGY. 205 

SUPRARENALE 

The suprarenals are two small bodies of a 
somewhat triangular shape which surmount the 
kidneys. 

They are about 1-J in. in height and 1£ in. in 
width. They weigh 1 to 2 drms. each. 

Structure. — They are invested by a fibrous 
coat which surrounds each organ. On section, 
they are seen to consist of a cortical portion 
forming the greater part of the organ, of firm 
consistence and yellow color, and a medullary 
portion, which is soft and pulpy, and of a brown- 
ish black color. 

The Cortical Portion consists of a fibrous 
stroma, in the meshes of which are cells arranged 
in columns which radiate from the centre of the 
gland. The cells are granular, yellow, and 
nucleated, and are about 7-5V0 in. in diameter, 
and contain minute oil-globules. Small arte- 
ries run between the columns. 

The Medullary part is separated from the 
cortical by a layer of connective tissue, and is 
best marked in the suprarenals of young ani- 
mals. It consists of a stroma, in the meshes of 
which are enclosed groups of cells which are 
coarsely granular, have no oil-globules, and some 
of them are branched. 



206 MEMOKANDA OF PHYSIOLOGY. 

Nerves. — Bundles of nerves run through the 
cortex, and form a network in the medullary 
part. 

Function. — Nothing is known for certain re- 
garding the function of these bodies. The most 
interesting point is their connection with Addi- 
son's disease, in which tuberculosis of the 
suprarenal capsules is accompanied by a bronzed 
tint on the skin, vomiting, and progressive 
emaciation. Some maintain that, like the 
spleen, they exercise some influence in the elab- 
oration of nutritive material in the blood. 
Others believe them to be connected with the 
nervous system, and the cells of the medullary 
portion to be nerve-cells. 

THYROID GLAND. 

The thyroid gland consists of two lateral lobes 
situated on either side of trachea and larynx, 
and joined by an isthmus which crosses in 
front of the trachea at the third and fourth 
rings. It is soft, of a reddish color, and weighs 
from one to two oz., and is larger in the female 
than male. 

Structure. — It is invested by a layer of fibrous 
tissue which connects it with surrounding parts. 
It is composed of a number of closed vesicles, 



MEMORANDA OF PHYSIOLOGY. 



207 



which are from -g^-o in. in diameter to the size 
of a millet-seed. Each vesicle is surrounded by 
a plexus of capillaries, is formed of a basement 
membrane, and lined by a single layer of epithe- 
lium. They normally contain a clear fluid, but 
often a material of jelly-like consistence. The 
organ is very vascular, receiving a large blood- 
supply. 

Function. — Nothing is known concerning the 
function of the thyroid body. There are no 
facts to support the theory that, like the spleen, 
it pours white corpuscles into the blood. It is 
enlarged in certain diseases, as in goitre, com- 
mon in Derbyshire and the valleys of Switzer- 
land, and seems to be connected with the con- 
stant use of water impregnated with magnesian 
limestone ; and in exophthalmic goitre, a disease 
characterized by enlarged thyroid prominence of 
the eyeballs, and irregular action of the heart. 



Section 14. 

NEBVOUS SYSTEM. 

The Nervous System is divided into two 

great divisions : 

1. The Cerebrospinal. 

2. The Sympathetic. 

1. The Cerebrospinal includes the Drain, 
spinal cord, certain ganglia, motor and sensory 
nerves. The motor nerves are supplied to the 
striated or voluntary muscles, the sensory are 
distributed to the organs of sense, skin, and 
other parts endowed with sensibility. The 
nerve-fibres are mostly of the medullated kind. 

2. The Sympathetic consists of a series of 
ganglia and nerves, which supply the involun- 
tary muscular fibre of the uterus, stomach, in- 
testines, ducfcs, and blood-vessels. The sympa- 
thetic system has a less symmetrical arrange- 
ment than the cerebro -spinal ; the nerves are 



MEMORANDA OF PHYSIOLOGY. 209 

of a reddish color, and are composed, for the 
most part, of non-medullated or gray fibres. 

These two sections of the nervous system are 
intimately connected with each other, indeed 
they can hardly be regarded as distinct systems ; 
the sympathetic may be regarded as that portion 
of the nervous system which supplies the inter- 
nal organs and blood-vessels. 

Structure of the Nervous Mechanism. 

I. Purely conducting organs, nerves. 
II. Terminal end organs. 
III. Central organs, as brain, cord, ganglia. 

I. Nerves. 

Nerves consist of bundles of nerve-tubules or 
fibres bound together by a common connective- 
tissue sheath, called the epineurium. This 
sheath contains fibrous tissue, blood-vessels, nu- 
merous connective -tissue corpuscles, and has 
also lymph-spaces. 

If a transverse section of a large nerve, say 
the sciatic of a dog, be examined under the 
microscope, bundles of nerve-fibres will be seen, 
each bundle surrounded by its sheath (perineu- 
rium), and the bundles will be seen to be con- 
nected together by a coarser tissue containing 
vessels, and often adipose tissue (epineurium). 
U 



210 MEMOKANDA OF PHYSIOLOGY. 

Between the nerve-bundle and the perineurium 
is a space, which is lined by flattened cells, and 
forms the lymph-space ; it communicates with 
the lymphatics of the nerve. The nerve-tubules 
themselves are surrounded by fine connective 
tissue, containing numerous cells continuous 
with the perineurium. 

Each nerve-tubule will be seen in cross-sec- 
tion to consist of a central dot (axis-cylinder), 
surrounded by a clear material that does not 
stain with logwood or carmine (medullary 
sheath), enclosed by a ring (primitive sheath). 

Nerve-tubules are of two kinds : — 

(a) Medullated. 

(b) Non-medullated. 

(a) The Medullated Nerves are present, for 
the most part, in the cerebro-spinal system. 
They vary very much in size, being from -g-^xra to 
tooott in. in diameter. When examined shortly 
after death, they appear as translucent, homo- 
geneous threads with a single contour. On ad- 
dition of various reagents, it can be made out 
that a medullated nerve consists of : 

(1) Primitive nerve-sheath. 

(2) White substance of Schwann. 

(3) Axis-cylinder. 



MEMORANDA OF PHYSIOLOGY. 211 

(1. ) The 1 primitive nerve-sheath or neurilemma 
is a thin hyaline membrane which surrounds the 
nerve -tubule. In this sheath annular constric- 
tions may be seen at intervals, which project 
into the nerve-tubule as far as the axis- cylin- 
der ; these constrictions are called the nodes 
of Ranvier. On the inner surface of the sheath 
are nuclei surrounded by finely granular proto- 
plasm ; these nuclei do not belong to the neuri- 
lemma. 

(2. ) The medullary sheath is semi-fluid during 
life, but coagulates after death. It consists of 
fatty matters, soluble in ether, and when 
squeezed out of the primitive sheath appear 
like bright drops with a dim contour. When 
the white substance has coagulated, the nerve, 
which immediately after death appears to have 
a single outline, becomes dark-bordered. Ac- 
cording to Klebs, the axis- cylinder and medul- 
lary sheath are separated by a narrow space, 
called the periaxial space, containing a cement 
substance. The medullary sheath is stained 
black by osmic acid. 

1 (1) The epineurium is a coarse, fibrous sheath which 
surrounds the whole nerve and binds the bundles or strands 
together. (2) The perineurium surrounds each strand or 
bundle. (3) The primitive nerve-sheath is a fine mem- 
brane which forms the sheath of each nerve-tubule. 



212 MEMORANDA OF PHYSIOLOGY. 

(i>.) The Axis-cylinder is a narrow thread 
which runs through the centre of the nerve. 
It is albuminous in nature, is continuous with 
the poles of nerve-cells, and stains with car- 
mine, logwood, chloride of gold, or, better than 
all, aniline blue-black. 

Medullated nerves when coming near their 
terminations lose their medullary sheath. Some 
medullated nerves, especially in the optic nerve, 
possess more or less regular varicose enlarge- 
ments. 

(b) Non-medullated Nerves consist of : 

(1) Primitive nerve-sheath. 

(2) Axis-cylinder. 

They closely resemble the medullated nerves, 
but the white substance of Schwann is wanting. 
They vary in size touu to ^htu in. in diameter. 
They are present for the most part in the nerves 
of the sympathetic system, but they are also 
present in the cerebro-spinal nerves. 

II. Terminal End Organs. 

(A.) Sensory Nerves end in: 
1. Networks or plexuses. 



MEMORANDA OF PHYSIOLOGY. 213 

r (a) Pacinian bodies. 
(b) End-bulbs. 
2. Special Organs, -j (c) Touch-corpuscles. 

(d) Rods and cones, taste- 
buds, &c, &c. 

(B.) Motor Nerves: 

1. Striated muscle. 

2. Non-striated. 

I. Sensory Networks or Plexuses. — The 
nerve-bundles as they approach their termina- 
tions divide and re- divide till the branches con- 
sist of only one or two tubules. In the skin 
and mucous membrane, when the nerves are ap- 
proaching the surface epithelium, they lose 
their medullary sheath, join together, and form 
the subepithelial plexus. From this plexus fine 
fibrils are given off, which, according to Klein, 
pierce the rete mucosum, and end beneath the 
cells of the horny layer, or, according to some, 
in the epithelial cells themselves. 

In the cornea there are.two terminal plexuses, 
superficial and deep. The superficial forms a 
subepithelial plexus, which gives off minute fib- 
rils, which end in the interstitial substance be- 
tween the epithelial cells on the surface. The 
deep plexus is situated in the substance of the 



214 MEMORANDA OF PHYSIOLOGY. 

cornea ; some of the fine fibrils are said to end 
in the corneal corpuscles. 

2. Special Organs — (a) Pacinian Bodies are 
ovoid in shape, about -^ to - 2 L 5 - in. in diameter, 
and are found attached to the digital, plantar, 
pudic, infra-orbital nerves and mesenteric nerves 
of the cat. These bodies consist of a number of 
concentric membranes placed inside each other, 
enclosing- a clear space in the centre, which 
contains the termination of a nerve. Each cap- 
sule consists of a hyaline membrane marked 
with fine transverse fibres, and lined on their 
inner surface by a layer of endothelial cells. 
There is no fluid between the layers, as some- 
times described. The central clear mass con- 
tains a hyaline matrix and an axis-cylinder, the 
sheath and white substance of Schwann being 
lost before the nerve enters the clear space. 
Besides the nerve a minute artery enters the 
Pacinian body, and distributes capillaries be- 
tween the capsules. 

(5) Bnd-Bulbs exist in man in the conjunc- 
tiva, lips, mucous mernbrane of mouth, soft 
palate, genital organs. They are about -^oo in. 
in diameter, and consist of an ovoid corpuscle, 
in which a medullated nerve-fibre terminates. 
They are surrounded by a capsule continuous 
with the perineurium surrounding the nerve. 



MEMOKANDA OF PHYSIOLOGY. 215 

The matrix is a granular mass containing oval 
nuclei. The nerve loses its medullary sheath 
and ends in a bud-like process. 

(c) Touch- Corpuscles exist in the skin in 
the papilla or beneath the epithelium in other 
situations. They are about ^oo m - m diameter, 
and consist of a capsule, with a core of granular 
matter, which receives an axis-cylinder after a 
more or less tortuous course, (d) Other end 
organs, as the rods and cones, taste-buds, or- 
gan of Corti, will be described in connection 
with sight, taste, etc. 

(B.) Terminations in Muscles. — (l)Non stri- 
ated muscles are supplied with non-medullated 
nerves, which form plexuses. These plexuses 
give off the primitive fibrils which run in the 
interstitial substance between the cells ; and, 
according to some, give off fine branchlets, 
which enter the nuclei of the cells themselves. 

2. Striated Muscle. — Nerves surrounded by 
their perineurium run in the connective tissue, 
forming the sheath of the muscle. Branches 
are given off which form a plexus, branches 
containing two or three nerve -tubules form an 
intermediate plexus for the supply of the 
smaller bundles of fibres. The nerve-tubules 
enter the muscular fibres, the primitive sheath 



216 MEMORANDA OF PHYSIOLOGY. 

becomes fused with the sarcolemma, while the 
axis- cylinder loses its medullary sheath and 
passes through the sarcolemma. The axis- 
cylinder ends on the surface of the muscle sub- 
stance embedded in a flat granular mass, the 
end-plate of Kuhne. The end-plates viewed in 
profile form Doyere's prominences. 

III. Structure of the Central Organs. 

The Gray Matter is present on the surface of 
the convolutions of the cerebrum, cerebellum, in 
the central parts of the spinal cord, corpora 
striata, optic thalamus, corpora quadrigemina, 
ganglia, etc. 

It consists of : 1. Nerve-cells. 2. Nerve- tu- 
bules. 3. Pigment. 4. Blood-vessels. 5. Neu- 
roglia. 

White Substance consists of: 1, Nerve-tu- 
bules. 2. Blood-vessels. 3. Neuroglia. 

1. Nerve-Cells are small, rounded or 
branched bodies, destitute of a cell- wall, formed 
of finely granular protoplasm, in reality consist- 
ing of a fine network of fibrils. Each cell con- 
tains a nucleus, having a well-defined capsule, 
fine network, and a nucleolus. The cells are 
surrounded by a perivascular space. In shape 
they are apolar, unipolar, bipolar, or multipolar, 
according to the number of processes they pos- 



MEMORANDA OF PHYSIOLOGY. 217 

sess. Each process is continuous with the axis- 
cylinder of a nerve. Apolar cells are found in 
the sympathetic ganglia, unipolar in the cere- 
bellum and cord, dipolar in the ganglia on the 
posterior roots of the spinal cord, tripolar in the 
gray matter of the cerebrum, and multipolar in 
the spinal cord. 

Neuroglia. — This name is given to the frame- 
work of the gray and white matter of the cere- 
brum, cerebellum, and cord. It consists of : 
(1) Branching nucleated cells. (2) A fine net- 
work of fibrils connected with the branches of 
the cells. (3) A homogeneous or finely granu- 
lar matrix. The neuroglia forms a material in 
which the nerve-cells and fibres are embedded ; 
it slightly varies in different parts of the nervous 
system. 

The white matter is distributed in various 
places in the brain and cord, connecting the gray 
matter of different parts. The nerve-fibres are 
medullated, but have no primitive sheath. They 
vary in size, often possess varicose swellings, 
due to an accumulation of fluid between axis- 
cylinder and medullary sheath. 

Ganglia. — These consist of rounded or elon- 
gated bodies found in various situations in con- 
nection with nerves. They are present in the 
following places : 



218 MEMOBANDA OF PHYSIOLOGY. 

1. On the posterior roots of the spinal nerves ; 
on the roots of the 5th, 7th, vagus, glossopha- 
ryngeal ; in several other situations, as the 
ophthalmic, Meckel's otic, and lenticular gan- 
glia. 

2. In connection with the sympathetic sys- 
tem, (a) forming a series by the side of the 
vertebral column ; (b) in numerous other places 
in the walls of the heart, intestines, uterus, and 
in connection with the plexuses. 

They consist of gray matter, the nerve-cells 
having mostly a pyriform or rounded outline. 

PROPERTIES AND FUNCTIONS OF 
NERVES. 

1. Nutrition. — Nervous matter receives a rich 
supply of blood ; the network of capillaries in 
the gray matter is closer than in the white. The 
nerve -cells receive their nourishment from liq. 
sanguinis which has exuded from the vessels. 
Active nerve-cells absorb O and eliminate C0 2 . 
Some nerve-centres exercise an important in- 
fluence over the nutrition of certain^ nerves ; 
thus, if a motor nerve of the spinal cord is cut 
off from the gray matter in the anterior cornua, 
it undergoes fatty degeneration, and the muscle 
it supplies becomes atrophic. If a sensory nerve 



MEMOEANDA OF PHYSIOLOGY. 219 

is divided, the part attached to the posterior 
ganglion remains normal ; that part which 
has been separated from the ganglion degen- 
erates. 

When a nerve is cut in a mammal, the ends 
often reunite in a few weeks. 

2. Nervous Excitability and Conduc- 
tivity. — Nerves, like muscles, are irritable or 
excitable. If one end of a nerve is irritated by 
the application of a stimulus, such as the appli- 
cation of heat, the electrodes of a battery, or 
by other means, the irritation or excitation is 
conveyed along the nerve to its farthest ex- 
tremity. If the nerve is attached to muscular 
fibre, a contraction is produced ; if the nerve 
ends in a sensory centre, a sensation is produced, 
or the secretion of a gland poured out if the 
nerve terminates there.\ The nerves receive 
impressions through the medium of certain ter- 
minal organs, as the touch-corpuscles, rods and 
cones of retina, and convey the impression pro- 
duced to a certain sensory centre, and a sensa- 
tion is felt, or they receive an impulse from cer- 
tain motor centres, and convey the impulse to 
their terminations in the end-plates of the mus- 
cles and a muscular contraction ensues. 

If the nerves are too frequently excited they 
become fatigued, and a certain amount of re- 



220 MEMOKAKDA OF PHYSIOLOGY. 

pose is necessary for them again to conduct im- 
pressions. 

There are several methods of measuring the 
velocity of the nerve-current. The ordinary 
method in motor nerves of frog consists in ap- 
plying the electrodes directly to the muscle, and 
measuring the time that elapses before the con- 
traction, the contracting muscle recording its 
movements by means of a lever on a revolving 
drum (a chronograph marking time) ; then, if 
the electrodes be applied to the nerve, at some 
distance from the muscle, and the time again 
measured, it is evident that the difference be- 
tween the two will be the time that the nerve- 
current took to travel through the nerve. 

The velocity of the nerve-current has been 
calculated to be about 80 feet per second in the 
frog, and 100 to 120 feet, per second in man, 
though some placed it at 200. Sensory impres- 
sions in man have been measured in the following' 
way: Arrangements are made for a person to 
give a signal — the moment he feels a prick, say, 
on his great toe — and the time noted between 
the prick being administered and the signal 
given. Another experiment is made in the same 
way by pricking a point nearer the brain, say the 
knee, and the time measured. The difference 
between the two will be the time the impression 



MEMORANDA OF PHYSIOLOGY. 221 

takes to travel from toe to knee. It has been 
found that the velocity is about the same as in 
motor nerves — 110 to 120 feet per second. This 
method is, however, open to many objections. 

3. Electrical Phenomena of Nerves. — Elec- 
trical currents are present in living nerves. If 
a piece of a nerve be cut out and placed upon 
the electrodes of a galvanometer, so that the 
surface of the nerve touches one electrode 
and the cut end the other, a current will be ob- 
served to pass from the surface through the 
galvanometer to the cut end. The nerve- cur- 
rents exactly resemble the muscle-currents. 
When the nerve is excited there is a diminution 
or negative variation of the normal current. 

Blectrotonus. — If a constant current be 
passed along a nerve, the nerve is thrown into 
a peculiar state termed electrotonus. If the 
current travel in the direction of the natural 
nerve -current, the latter is increased ; if in the 
contrary direction, it is diminished. 

While a portion of nerve is traversed by the 
constant current, its properties are to some ex- 
tent altered ; the portion in the neighborhood 
of the positive pole is said to be in an anelectro- 
tonic state, while the portion of nerve in the 
neighborhood of the negative is in a cathelec- 
trotonic state. The position of the neutral 



222 MEMORANDA OF PHYSIOLOGY. 

point between the two varies with the strength 
of the current passing through the nerve. With 
a current of medium intensity, the neutral point 
is midway between the poles ; with a weak cur- 
rent the neutral point is nearer to the positive 
than the negative ; with a strong current the 
neutral point is nearer the negative than the 
positive. "When a nerve is in the anelectrotonic 
state, its natural nerve-currents are increased, 
but its excitability and conductivity are dimin- 
ished. When in the cathelectrotonic, its natural 
nerve-current is diminished, but its conductivity 
and excitability are increased. 

Pfliiger's Law of Contraction.— When a 
constant current of medium strength is passed 
along a motor nerve, no effect is produced upon 
the muscle, except on opening and closing the 
current. The contraction of the muscle is in- 
fluenced (1) by the direction, (2) by the strength 
of the current — that is, the strength of the 
contraction on making and breaking contact 
varies not simply according to the strength of 
the current applied, but also to the direction, 
whether the current is passed downward in a 
direction from the spinal cord to the muscle, or 
in an upward direction from the muscle to the 
cord. The following is a brief statement of 
the facts : 



MEMOKANDA OF PHYSIOLOGY. 



223 



Strength of Current. 


Descending. 


Ascendin jr. 


Make. 


Break. 

R 
R 

C 
R 


Make. 

R 

C 

c 

R 


Break. 


Very weak 


c 

c 
c 
c 


R 


Weak 


R 


Medium 


c 


Strong 


c 







(^contraction. R— rest. 



From this table it will be seen that, if either 
a weak or a strong current is passed along a 
motor in a downward direction, there will be a 
contraction at making only. With a strong as- 
cending current there is a contraction on break- 
ing only. 

Functions and Classification of Nerves. 

Nerves are divided according to their func- 
tions into— I, Efferent ; II. Afferent. 

I. The Efferent nerves are divided according 
to their uses : (1) Motor fibres, at the peripheral 
end of which is a muscle. (2) Vaso-motor fibres, 
which supply the muscular fibres of the blood- 
vessels. (3) Secretory, which are supplied to 
the epithelium cells of glands. (4) Inliib- 
iiory nerves, which modify the action or inhibit 



224 MEMOKANDA OF PHYSIOLOGY. 

the centres to which they are supplied. (5) 
Connecting motor cent v es. 

II. The Afferent nerves may be divided into 
— (1) Sensory, which convey sensations of pain 
or pleasure, hearing, sight, touch ; and (2) Con- 
necting sensory centres. 

Eccentric Reference of Sensations. — The 
mind refers the origin of every sensation that 
reaches it through a sensory fibre to the end 
organ of that fibre, even though stimulation has 
been applied to the trunk of the nerve. Thus, 
persons whose arms or legs have been ampu- 
tated often feel sensations which they refer to 
their fingers or toes. Any stimulation of the 
optic nerve, mechanical or electrical, the mind 
refers'to the action of light upon the retina. 

Functions of Terminal Organs. — Probably 
all nerves end at their peripheral distribution 
in some form of terminal organ. The optic 
nerves are connected with the rods and cones of 
the retina, and other sensory nerves are con- 
nected with taste-bulbs, olfactory corpuscles, 
tactile corpuscles, or epithelium. Motor nerves 
end in end-plates inside the sarcolemma. Light 
will not affect the optic nerves, except through 
the medium of the rods and cones ; sensations 
of touch will not be received at the brain if the 
skin is stripped off the fingers. The terminal 



MEMORANDA OF PHYSIOLOGY. 225 

organs seem to play the part of receivers of 
impressions, and awaken an excitation in the 
nerves connected with them. 

Functions of Nerve-Centres. 

Groups of nerve -cells, which form the nerve- 
centres, are arranged in the body in two sys- 
tems, the cerebro-spinal and the ganglionic 
system, consisting of ganglia scattered through 
the body. The centres may be classified in 
various ways, according to their functions ; 
thus, on the surface of the brain there are 
motor or. discharging centres, centres of special 
sensations, as of sight, touch ; in the medulla 
there are inhibitory and accelerating centres. 
They all, however, fall into two great divisions, 
though it is not always easy to say to which 
class they belong. These are automatic centres 
and reflex centres. 

Automatic Actions are actions which are 
evoked in the absence of any influence external 
to the nerve-centre. The brain is the seat of 
the higher automatic centres, those connected 
with volition and intelligence. In the medulla 
the respiratory centres, cardiac centres, vaso- 
motor centres, are in a certain sense automatic. 
So are also the intrinsic ganglia of the heart, 
and the small ganglia found in the walls of the 
15 



226 MEMORANDA OF PHYSIOLOGY. 

intestines. At the same time it must be re- 
membered that many of the centres enumerated 
above are influenced by sensory or afferent im- 
pulses, and are reflex as well as automatic ; in- 
deed, some would deny them their automatism, 
and believe that no motor impulses can be gen- 
erated, in the absence of all eccentric influ- 
ences. 

Reflex Actions. — For reflex actions the fol- 
lowing apparatus is required : 

(1. ) A sensory surface in connection with an 
afferent nerve. 

(2.) A group of nerve-cells. 

(3. ) An efferent nerve connected at its central 
end with (2) and by its peripheral end with 
some muscle or muscular tissue. The sentient 
surface or end organ being excited, the impulse 
travels along the afferent nerve to the centre, 
and is reflected from the centre along the effer- 
ent nerve to the muscle. 

Reflex actions may take place without evok- 
ing consciousness, and may be entirely beyond 
the control of the will. Such an act is the con- 
traction of the pupil under the influence of 
light. Some other reflex actions we are more 
or less conscious of, and can control or modify 
by our voluntary powers, such as the act of 
respiration or coughing. Some acts we are con- 



MEMOEANDA OF PHYSIOLOGY. 227 

scious of, but cannot control, as sneezing, vom- 
iting. The character of the efferent impulses 
may either depend upon the intensity of the 
stimulus applied, or the energy stored up in the 
nerve-centre, and be out of proportion to the 
intensity of # the stimulus. Thus, in a brainless 
frog, if the skin of the flank be irritated, a 
slight movement of the muscle beneath fol- 
lows ; if the stimulus is increased, the hind leg 
of the same side endeavors to remove the irrita- 
tion ; subsequently, if the irritation be still 
greater, all the muscle of the body, including 
those of the limbs of opposite side, will en- 
deavor by their actions to get rid of the source 
of irritation. On the other hand the irritation 
caused by the presence of a hair in the glottis 
will call into play a large number of expiratory 
muscles, though the irritation would seem to be 
so small in amount. 

The following instances of reflex acts may be 
taken as examples : 

(1.) Contraction of iris. A.N. — optic. N.C. 
=z corpora quadrigemina. E.N. third. 

(2.) Winking. A.N. = fifth or optic. N.C. 
= corpora quadrigemina. E.N. seventh. 

(3) The first respiration after birth from im- 
pression of cold on the skin. ANs. = sensory 



228 MEMORANDA OF PHYSIOLOGY. 

of cord. N.C. = medulla. ENs. phrenics, in- 
tercostals, etc. 

(4.) Vomiting from tickling the fauces. ANs. 
= glossopharyngeal, fifth. N.C. medulla. ENs. 
phrenics, Ns. to abdominal muscles, vagi, 

(5.) Sneezing from a draught of cold air. 
A.N. = nasal branches of fifth. N.C. = med- 
ulla. ENs. intercostal s, Ns. to abdominal mus- 
cle, phrenics, etc. (See also p. 117.) 

Reflex actions are also seen in various forma 
of disease or abnormal conditions, such as vom- 
iting from cerebral tumor, Vomiting of preg- 
nancy, grinding of teeth from irritation of 
worms, palpitation of heart, etc. 

Strychnine excites reflex actions by stimulat- 
ing the centres. Bromide of potassium de- 
presses the centres and diminishes reflex sen- 
sibilities. 

THE SPINAL CORD. 

The Spinal Cord has its upper limit at the 
margin of the occipital foramen, and extends 
downward to the lower border of the first lumbar 
vertebrae. It is fifteen to eighteen inches in 
length, and presents two enlargements, the cer- 
vical and lumbar. It ends below in the cauda 
equina, which consists of a bundle of nervous 
cords. 



MEMORANDA OF PHYSIOLOGY. 229 

Structure. — The cord consists of: 

(1) The gray matter in the centre. 

(2) The white substance externally. 

(1.) The Gray Matter consists of two cres- 
cents, joined by a commissure, in the centre of 
which is the central canal of the spinal cord. 
The anterior cornua of the crescents are 
rounded, and connected with the anterior roots ; 
the posterior are more pointed, and connected 
with the posterior. 

The cells of the anterior cornua are large, 
Too to 200" mcn m diameter, are multipolar, 
and contain nuclei and pigment ; some of the 
cells are small and round. In the posterior 
cornua, the cells are collected into two groups, 
the substantia gelatinosa at the extremity of 
the cornua, and the posterior vesicular column 
situated on the inner side of the cornua near 
the commissure. Many of the cells in the pos- 
terior cornua are destitute of processes. 

(2.) The White Matter is divided into two 
halves by the anterior and posterior fissures. 
Each lateral half is again divided by two lateral 
fissures, which are merely grooves along the line 
of attachment of the anterior and posterior 
branches into an anterior, lateral, and posterior 
column. The white substance on section, and 



230 MEMOKANDA OF PHYSIOLOGY. 

examination by a high power, displays the cut 
ends of the nerve-fibres, presenting small rings 
with a dot in the centre. The dot representing 
the axis-cylinder, and the surrounding space the 
white substance of Schwann. 

Functions of the Cord. 

(1.) As a conductor of impressions and im- 
pulses. 

(2.) As a series of nerve-centres. 

The Cord as a Conductor. 

(1. ) The spinal cord forms the channel of com- 
munication between the brain and nerves pass- 
ing to the periphery of the body. The exact 
path of the motor and sensory nerves is not 
definitely settled, as there is still a difference of 
opinion among experimenters. 

Motor Path. — The motor impulses travel 
along the lateral columns of the cord, their de- 
cussation taking place in the medulla only. The 
fibres pass from the anterior pyramid of one 
side to the lateral column of the opposite side, 
and join the anterior roots of the spinal neives. 

Sensory Path — The sensory nerves pass into 
the cord by the 'posterior root; the sensations of 
pain, temperature, etc., travel upward along 
the central gray matter, those of touch along 



MEMORANDA OP PHYSIOLOGY. 231 

the posterior columns ; the decussation taking 
place immediately the nerves enter, the sensa- 
tion travelling up the opposite side of the cord. 

According to Ludwig the sensory impres- 
sions travel along the lateral columns with the 
motor, the anterior and posterior columns being 
simply commissural, connecting different por- 
tions of the cord together. 

If one lateral half of the spinal cord be di- 
vided there will be loss of motion on the same 
side, and loss of sensation on the opposite. 

Reflex Functions of the Spinal Cord. 

(2.) Frog. — If the spinal cord of a frog be di- 
vided immediately below the occipital foramen, 
the frog will retain its usual sitting attitude, with 
the exception of sinking down into a somewhat 
less erect position, the fore limbs being more 
spread out. It will exhibit no respiratory move- 
ments. If one of the hind legs be pulled out 
straight and let go, it will be drawn up again to 
its normal position. If the skin of one flank be 
tickled, the muscle beneath will contract. 
Pinch the same spot, or apply a drop of acetic 
acid, and the leg of the same side will make a 
sweeping movement to clear away the source of 
irritation ; if the leg of the same side be held 
or cut off, the leg of the other side will repeat 



232 MEMORANDA OF PHYSIOLOGY. 

the movement. Place the frog on its back, it 
will make no effort to regain its position. The 
above actions of the brainless frog are compli- 
cated, co-ordinated, purposeful in character ; 
but, however stimulated, the animal never leaps. 

In the Mammal. — For some days after the 
division of the cord in a dog, very feeble re- 
actions are given by the nervous mechanism of 
the cord. After some weeks, movements of a 
varied character are evoked by tickling or pinch- 
ing the toes. 

In man, when the cord is crushed from the 
effects of accident or disease, the legs will start 
up on tickling the soles or in passing water. 
In the normal condition, it is generally possible 
to evoke reflex actions of the cord by gentle 
stimulation of the skin by a touch or light 
stroke. Tickling the soles of the feet, more 
particularly during sleep, will cause a slight 
withdrawing movement of the muscles of the 
foot, called the ''plantar reflex. " The centre 
for this movement is situated in the lower part 
of the lumbar enlargement. Irritation of the 
skin of the buttock will often produce a con- 
traction of the glutei (gluteal reflex), the nerve- 
centre being situated at the origin of the fourth 
or fifth lumbar nerves. Irritation of the inner 
side of the thigh will cause a contraction of the 



MEMORANDA OF PHYSIOLOGY. 233 

cremaster (cremasteric reflex), drawing up the 
testicles, the centre being connected with the 
first and second lumbar nerves. There is also 
an abdominal reflex and an epigastric reflex, 
which may be produced by stroking the side of 
the abdomen and side -of the chest respectively. 
The "patellar reflex" is obtained by allowing 
the knee to swing freely, and then sharply tap- 
ping the patellar tendon, the leg jerking for- 
ward ; the nerve-centre for this movement is 
situated in the upper part of the lumbar en- 
largement of the cord. 

Inhibition of Reflex Actions. — The brain 
exercises a powerful influence in restraining or 
inhibiting reflex actions. A brainless frog ex- 
hibits reflex actions better than one with brain 
intact. If the experiment be tried of suspend- 
ing a frog with cerebral hemispheres only re- 
moved, with its toes dipping in dilute acid, and 
the time which elapses before their withdrawal 
noticed, and the same experiment repeated, 
stimulating the optic lobes at the same time, 
the time elapsing before the withdrawal will be 
prolonged, showing the optic lobes have inhib- 
ited the reflex centres. 

Man, by an effort of will, can prevent the 
withdrawal of his feet if the soles are tickled. 



"A 3& MEMORANDA OF PHYSIOLOGY. 

Special Centres in the Spinal Cord. 

(1) Centre for maintaining tonus of the 
muscles. 

(2) Centre for sphincter of bladder. 

(3) Centre '* rectum. 

(4) Centre of contractions of uterus. 

(5) Centre for erection of genital organs. 

(1) The muscles of the body are kept in a 
constant state of contraction or tonus; this 
effect is due probably, not to an automatic, but 
to a reflex mechanism constantly occurring. 

(2) (3) Centres for micturition and defeca- 
tion appear to exist in the lumbar region of the 
spinal cord. 

(4) (5) The centres that govern the move- 
ments of the uterus and erectile tissues are sit- 
uated in the lumbar region of the cord. 

The above centres are to be considered reflex 
rather than automatic. 



THE MEDULLA OBLONGATA, 

TnE medulla is bounded above by the lower 
border of the pons Varolii, and is continuous 
below with the spinal cord at a level with the 
foramen magnum. 



MEMORANDA OF PHYSIOLOGY. 235 

Structure. — The medulla is divided on the 
surface by fissures into short columns, which 
have received different names. Each lateral 
half having from before backward : 

Anterior pyramid. 

Olivary body. 

Lateral tract. 

Bestiform body. 

Posterior pyramid. 

These short columns consist for the most part 
of white matter, and are in direct continuity 
with the fibres of the columns of the cord, with 
the exception of the olivary body. The fol- 
lowing tables show their connection with the 
spinal cord and brain. 

Medulla. Spinal cord. 



Anterior pyramids. -! 



Anterior column of same side. 
Lateral column of opposite .side. 



( Anterior column (small part). 
BESTIFORM bodies ...< Lateral column. 
( Posterior column. 

Posterior pyramids. Posterior (median) column. 

Spinal cord. Medulla. Brain. 

'1. Part of restiform 

body Cerebellum. 

Anterior , 2. Forms fillet of oli- 

column vary body Corpora quadrigemina 

3. Anterior pyramid 
i , same side Cerebrum. 



236 MEMOEANDA OF PHYSIOLOGY. 

Spinal cord. Medulla. Brain. 

fl. Part of restiform 

t , ™.r> . T bod y Cerebellum. 

L ™ \ 2- Anterior pyramid 
oiiU * of opposite side . . Corpus striatum. 

1^3. Fasciculus teres.,. Optic thalamus. 

fl. Part of restiform 
Posterior I ho ^ Cerebellum. 

column 1 2 ' Post f ri01 : *™ •' 
, and ]omg fasci _ 

cuius teres Optic thalamus. 

The gray matter of the medulla is scattered 
through its substance, forming the numerous 
centres. 

Functions of the Medulla. 

(a) Conductor of impulses and impressions. 

(b) As a collection of nerve-centres. 

(a) The Medulla as a Conductor. 

The Motor impulses travel through the an- 
terior pyramids, decussating to the lateral col- 
umn of the opposite side of the cord. 

The Sensory path is not so well known, but 
not improbably it lies along the fasciculi teretes 
— small bands of white matter situated in the 
floor of the fourth ventricle, and formed by a 
continuation upward of the lateral columns and 
posterior pyramids. 



MEMORANDA OF PHYSIOLOGY. 237 

(5) Nerve-Centres in the Medulla. 

(1) Respiratory centres. 

(2) Vaso-motor centre. 

(3) Cardiac centres. 

(4) Centres for deglutition. 

(5) Centre for voice. 

(6) u " mastication 

(7) u iC expression. 

(8) u u salivary secretion. 

(1.) The respirator?/ centres consist of an in- 
spiratory and expiratory centre, and are both 
reflex and automatic. Ordinary respiration is a 
reflex act ; a venous condition, f.&, a want of 
O in the blood circulating through the capil- 
laries of the lungs, stimulates the terminal 
fibres of the vagus, the vagus transmits the 
impression to the medulla, it is reflected along 
the phrenic, intercostals, etc. , to the muscles of 
inspiration, and a fresh supply of air is drawn 
into the lungs. The more venous the blood 
the more vigorously are the terminal fibres of 
the vagus excited, and the more muscles brought 
into play. If the vagi are divided the number 
of respirations sink to at least one- third, but 
they are still continued, and the animal does not 
die of asphyxia. It is probable that the venous 



238 MEMORANDA OF PHYSIOLOGY. 

blood supplied to the medullary centre itself 
excites it, or like the intracardiac ganglia, it 
acts in an automatic manner. 

(2.) The Vaso-motor Centre is the centre of 
the sympathetic system supplied to the muscu- 
lar fibre of the blood-vessels, intestines, ducts, 
etc. 

If stimulated, the vessels all over the body 
contract, and the arterial tension is raised ; if 
paralyzed or inhibited they dilate, and aiterial 
tension is lowered. The vaso-motor centre 
keeps the blood-vessels of the body in a state 
of tonic contraction, it acts reflexly, and any 
influence which inhibits it will dilate the ves- 
sels. 

(3.) Cardiac Centres. — The rythmical con- 
traction of the heart is caused by the action of 
its own intrinsic ganglia, but its action is regu- 
lated by ganglia situated in the medulla. 
There are two extra-cardiac ganglia, one accel- 
erating, acting on the heart through the sym- 
pathetic, and the other inhibitory, associated 
with the vagus. 

The presence of the above ganglia renders 
the medulla of vital importance to the living 
mammal. Death immediately results by de- 
stroying it. This can readily be accomplished 
by "pithing," i.e., by thrusting an awl-shaped 



MEMORANDA OP PHYSIOLOGY. 239 

instrument into the medulla, passing it between 
the occiput and atlas, and breaking up the ner- 
vous substance. 



STRUCTURE OF CORPORA QUADRIGEM- 
INA AND CEREBELLUM!. 

The Corpora Quadrigemina are four round- 
ed eminences, of which two, the nates, are in 
front, and two, the testes, are behind. They 
are represented in birds, reptiles, fishes, and 
some mammals by the optic lobes. In structure 
they are composed of white substance on the 
surface, and gray matter within. They are 
situated immediately above the aqueduct of 
Sylvius, are connected with the medulla by the 
fillet of the olivary body, with the cerebellum 
by its superior peduncles, and with the optic 
thalamus and optic tract by bands of white 
substance. 

The Cerebellum is situated at the posterior 
part of the brain, and consists of peduncles, 
various lobes and processes. The peduncles are 
three in number, the superior, middle, and in- 
ferior ; they serve to connect the cerebellum 
with the cerebrum, pons, and medulla respec- 
tively. 

The cortical portion consists of gray matter, 



240 MEMORANDA OF PHYSIOLOGY. 

and the central portion of white substance, with 
a nucleus of gray, the corpus dentatum. 

The cortical substance has three layers : 

(1.) External. — Consists of small cells spar- 
ingly distributed, some rounded, others irregu- 
lar in shape, with various processes; fibres 
which are for the most part processes of the 
large cells of the middle layer and run at right 
angles to the surface. 

(2.) Middle. — Consists of cells of Purkinje ar- 
ranged in a single layer. They are pyrif orm in 
shape, nucleated, and have long processes run- 
ning into the external layer, and are -g-Jro to 
Tooo mcn i n diameter. 

(3.) Inner or granule layer. — Consists of small, 
round, granular corpuscles, about the size of 
white blood-corpuscles, arranged in dense 
masses, which in stained specimens form a 
well-marked colored layer. 

Functions of the Corpora Quadrigemina. 

In man they contain (nates or subjacent 
structures) : 

(1.) Centres for co-ordination of the move- 
ments of the eyeballs. 

(2.) Centre for contraction of the pupils. 

In some of the lower animals they contain : 



MEMORANDA OF PHYSIOLOGY. 241 

(3.) Centres for co-ordination of retinal im- 
pressions with certain muscular movements. 

(4. ) Centre for maintenance of equilibrium. 

Ferrier found on applying a weak interrupted 
current to the surface of the nates in the mon- 
key, that irritation of one side caused the oppo- 
site pupil to become widely dilated, followed by 
dilatation of the pupil of same side. The eye- 
balls are directed upward and to the opposite 
side, and the ears retracted. The legs become 
extended, the jaws retracted, and angles of 
mouth retracted. Irritation of the testes pro- 
duces similar results, but in addition cries are 
elicited. 

Functions of the Cerebellum. 

Functions. — The principal function of the 
cerebellum, as far as known, is the co-ordina- 
tion of muscular movements in maintaining 
equilibrium. Every form of muscular exertion 
tends to overthrow the body and disturb the 
balance. It is found that animals that have 
the largest cerebella have the most complex 
muscular movements. In diseases of the cere- 
bellum the muscles are not paralyzed, there 
is no loss of sensation, but the movements are 
disorderly, and the gait awkward. 

When the anterior portion of the middle lobe 
16 



24:2 MEMORANDA OF PHYSIOLOGY. 

is injured, the animal tends to fall forward ; 
and backward when the posterior part is in- 
jured. Division of the middle peduncles causes 
the animal to rotate on its longitudinal axis 
toward the injured side. Each lateral half of 
the cerebellum presides over the muscular 
movements of the same side, the middle pe- 
duncle being connected with the motor tract of 
the opposite side in the pons above the decus- 
sation. It is doubtful if the cerebellum has any 
connection with the generative organs, as some 
have maintained. 

Ferrier found, on irritation of the upper sur- 
face of the cerebellum., movements of the eyes 
resulted, and also certain movements of the 
head and limbs. 

BASAL GANGLIA. 

The corpus striatum and optic thalamus are 
two bodies situated at the base of the brain, 
and projecting into the lateral ventricles. 

The Corpus Striatum consists of two masses 
of gray matter : (a) the intraventricular or 
caudate nucleus projects into the lateral ventri- 
cles ; (b) the extraventricular or lenticular nu- 
cleus is situated external and inferior, and is con- 
nected with the gray matter of the anterior 
perforated space and island of Reil. 



MEMORANDA OF PHYSIOLOGY. 243 

The Optic Thalamus consists of gray matter, 
and is situated behind the intraventricular nu- 
cleus. These ganglia communicate superiorly 
with the gray matter of the surface, and infe- 
riorly with the cord by means of the fibres of the 
crura, pons, and medulla. 

Functions. — Destruction of one of the corpora 
striata causes motor paralysis, while stimulation 
causes contraction of the muscles of the opposite 
side. An extravasation of blood into one of 
these ganglia gives rise to hemiplegia of the 
opposite side. The corpora striata are not the 
motor centres, but, being situated on the motor 
tract, if injured, paralysis results. Their office 
in all probability is the co-ordination of muscular 
movements in the performance of complex 
actions. Each act, for instance, in learning to 
dance, is dependent at first upon conscious 
efforb ; after a while the movements become 
habitual, and are performed without any atten- 
tion being required, and when the mind is 
otherwise engaged. Probably the corpora striata 
are the centres where these complex acts are 
rendered habitual and automatic movements 
organized. 

Destruction of one of the optic thalami is fol- 
lowed by loss of sensation on the opposite side, 
though this is denied by some. They are not 



244 MEMORANDA OF PHYSIOLOGY. 

the centres of sensation, though connected with 
jfche sensory path. They probably have the same 
relation to tactile as the corpora quadrigemina 
have to retinal impressions. 

THE CEREBRUM. 

The Cerebral Hemispheres form two ovoid 
masses of gray and white matter, with convolu- 
tions on their surface. The gray matter is mostly 
present on the surface, and forms a layer from 
i to i in. in depth, the amount being greatly 
increased by the convolutions. The white mat- 
ter is arranged in various ways, longitudinal 
fibres as the fornix, transverse fibres as the cor- 
pus callosum, peduncular fibres connecting the 
gray matter on the surface with the corpora 
striata (corona radiata), and the latter with the 
pons (crura). 

The gray matter of the cerebrum resembles 
the gray matter elsewhere, though the number 
and shape of the nerve -cells undergo consider- 
able variation. Five or more layers have been 
described," but they blend imperceptibly into 
one another. The most marked feature in their 
microscopic structure is the presence of cells 
resembling arrow-heads or elongated pyramids 
in the second and third layers, their apices being 



MEMORANDA OF PHYSIOLOGY. 245 

directed toward the surface. Multipolar and 
small round cells are present in the fourth and 
fifth layers. 

Functions. — The gray matter on the surface 
is the seat of the mind, including memory, in- 
tellect, volition, the emotions. It contains 
centres of special sense, sight, hearing, touch, 
smell, taste. Special motor centres, irritation 
of which produces contractions of the various 
muscles. (Ferrier. ) 

According to Ferrier, the special motor and 
sensory centres occupy the parietal lobe or its 
immediate neighborhood. By applying elec- 
trical currents to the brains of monkeys and 
excising certain portions, he has mapped out the 
various centres. He considers the frontal lobes 
are connected with the intellectual faculties, and 
the occipital with the organic sensations, as 
hunger and thirst. Ferrier's conclusions, while 
interesting and important, have not as yet been 
universally accepted. 

Aphasia. — The term aphasia is applied to a 
condition in which patients (who at the same 
time are for the most part suffering from right 
hemiplegia), have lost the faculty of speech. 
There is no paralysis of tongue or lips, no loss 
of the mental faculties, but the patient has lost 
the power of expressing himself in words. This 



246 MEMORANDA OF PHYSIOLOGY. 

condition is generally found associated with a 
lesion of the posterior portion of the third frontal 
convolution. (Broca.) 

Phenomena Exhibited after Removal of 
Cerebral Hemispheres. 

Frog. — After the removal of the cerebral 
hemispheres, the animal maintains its normal 
attitude. If laid on its back, it will ■ turn over 
and regain its feet. If its foot is pinched, it 
will hop away. If thrown into water, it will 
swim, reach the edge, clamber up and sit per- 
fectly still. If its back is stroked it will croak. 
If placed in water and the temperature raised, 
it will make efforts to escape. If it jump away 
after a stimulus has been applied, it will avoid 
any object in its path. It will never move with- 
out some stimulus being applied. All sponta- 
neous action has departed. It will not feed 
itself, but will sit still till it decomposes. 

Fish exhibit similar phenomena, they swim 
about in the water, but the movements are not 
vo 7 untary, but result from the stimulus of the 
water in contact with the body. 

The Pigeon, with cerebral hemispheres re- 
moved, sits on its perch and balances itself per- 
fectly. When thrown in the air it flies, when 
pinched it moves forward. If not meddled with 



MEMORANDA OF PHYSIOLOGY. 247 

it appears to be in a profound sleep, though 
occasionally it will dress its feathers or yawn. 
Its pupils contract normally. It resists any 
efforts made to open its beak, but swallows 
when food is placed in its mouth. It makes 
no spontaneous movements ; the yawning and 
dressing itself are probably the result of the ir- 
ritation of the wound. 

Babbit. — When the cerebral hemispheres are 
removed, the animal is at first prostrate. After 
a while the animal can use its legs, though the 
fore ones are weak. If pinched it springs for- 
ward, but, unlike frogs in a similar condition, 
will strike itself blindly against any obstacles 
in its path. When pinched severely it utters 
cries. 

In higher animals, as cats and dogs, motor 
paralysis is so marked after the removal of the 
hemispheres, that no conclusions concerning 
equilibrium and co-ordinated movements can be 
drawn. 

At first sight it would appear that conscious- 
ness was necessary for the performance of com- 
plicated movements and the avoidance of ob- 
jects in the path ; the cries elicited on pinching 
would appear to indicate the sensation of pain. 
Probably they are the result of a reflex mechan- 
ism, and are similar to walking during sleep, or 



248 MEMOEANDA OF PHYSIOLOGY. 

the cries elicited from patients when under 
chloroform. The medulla contains centres for 
reflex actions more complicated than the cord, 
and the corpora quadrigemina and cerebellum 
contain centres for still more complex acts, as 
the reflex expression of emotion, the avoidance 
of an object when leaping, or the co-ordination 
of many contracting muscles. 

MOTOR AND SENSORY PATHS. 

The path by which impulses originating in the 
motor centres of the cerebrum reach the mus- 
cles, and the path by which sensations reach the 
centres from the periphery, are not definitely 
settled. The following summary shows the 
route so far as known : 

Motor path. Sensory path. 



Gray matter of surface. 

Corpus striatum. 

Crnsta. 1 

Anterior pyramids. 

Lateral columns (opposite 

side). 
Anterior roots. 
Motor nerves. 
Muscles. 



Skin. 

Sensory nerves. 

Posterior roots and ganglia. 

Lateral columns ? 2 (opposite 

side). 
Fasciculi teretes ? 
Tegmentum. 3 
Optic thalamus. 
Gray matter surface. 



1 Crusta= superficial longitudinal fibres of pons and crura. 
3 See page 236. 

3 Tegmentum = deep longitudinal fibres of pons and 
crura. 



MEMOKANDA OF PHYSIOLOGY. 249 

FUNCTIONS OF THE CRANIAL NERVES. 

First, or Olfactory. — This is the nerve of 
smell, and is distributed to the upper third of 
the mucous membrane of the nose. 

Second, or Optic— This is the nerve of sight ; 
its fibres are acted on through the medium of 
the retina. 

Third, or Oculo-motor. — The third nerve is 
purely motor, being distributed to all the mus- 
cles of the eyeball, except the superior oblique 
and external rectus ; it also supplies the circu- 
lar fibres of the iris and the ciliary muscle. 
Paralysis of this nerve gives rise to ptosis ; that 
is, the eyelid droops in consequence of the un- 
opposed action of the orbicularis, the eyeball is 
turned outward and downward by the ext. 
rectus and sup. oblique, the pupil is dilated and 
fixed, and the eye cannot be accommodated to 
near objects. There is also double vision. 

Fourth. — Is purely motor, and supplies the 
superior oblique. 

Fifth, or Trifacial — (a) Ophthalmic, or first 
division^ is purely sensory to the eye and fore- 
head ; injury to this nerve causes ulceration and 
sloughing of the cornea, (b) Superior maxil- 
lary, or second division, is purely sensory to skin 



250 MEMORANDA OF PHYSIOLOGY. 

of face, mucous membrane of the nose, and 
teeth of upper jaw. Pungent odors, as of am- 
monia, are perceived through this nerve, (c) 
Inferior ', or third division , is sensory to the 
tongue, mouth, teeth, and skin covering lower 
jaw. It confers tactile sensibility on the tongue, 
and through it pungent and acid tastes, as of 
pepper, vinegar, and mustard, are perceived. 
Motor filaments are supplied to the muscles of 
mastication, including the buccinator, anterior 
belly of digastric, and mylo-hyoid. 

Sixth. — This nerve is motor to the external 
rectus. 

Seventh. — Includes the facial and auditory. 
The facial is motor and supplies the muscles of 
the face, lips, stylo-hyoid, digastric, soft palate 
(through the spheno-palatine ganglion), and ex- 
ternal musc'es of the ear. It is the special 
muscle of expression : when injured the corre- 
sponding side of the face becomes a blank, the 
mouth is oblique and dragged toward the sound 
side. The eye is wide open and cannot be 
closed ; food accumulates between the gum and 
cheek, and the pronunciation of labial conso- 
nants is difficult. It gives off the chorda tym- 
pani, the latter giving a small branch to the 
stapedius, and is distributed to the tongue and 
submaxillary glands. The chorda tympani prob- 



MEMORANDA OF PHYSIOLOGY. 251 

ably only influence taste through the medium 
of the salivary glands. The auditory is the 
special nerve of hearing. 

The Glosso-pharyngeal. — This nerve is mo- 
tor to the stylo- pharyngeus and constrictors. 
It is supplied to the circumvallate papillae, and 
is the special nerve of taste to the posterior sur- 
face of the tongue. It specially discriminates 
bitters and savory foods. 

The Vagus or Pneumogastric. — This nerve 
arises from the medulla, immediately below the 
glosso-pharyngeal. It contains both sensory and 
motor fibres, though part of the latter are de- 
rived from the spinal accessory. The vagus is 
distributed to three different sets of organs : 
(a) the lungs and respiratory passages; (b) 
the heart; (c) the pharynx, oesophagus, and 
stomach. 

(a) The superior laryngeal is the nerve of sen- 
sation to the mucous membrane of the larynx, 
and supplies one muscle — the crico-thyroid. 
Paralysis of this nerve causes loss of sensation 
in the larynx, and interferes with the utterance 
of high notes from paralysis of the crico-thyroid. 
The inferio?' laryngeal is the motor nerve to the 
intrinsic muscles of the larynx, except the crico- 
thyroid. Stimulation of the central end of the 
superior laryngeal causes a flaccid state of the 



252 MEMORANDA OP PHYSIOLOGY. 

diaphragm, and excites contractions of the ex- 
piratory muscles. The vagus supplies several 
different sets of fibres to the lungs, motor to the 
muscular fibre of the bronchi, ordinary sensory 
fibres, and fibres which, when stimulated, excite 
the contraction of the inspiratory muscles. 

(b) The vagus contains fibres which inhibit 
the action of the heart, by antagonizing the ac- 
tivity of the intracardiac ganglia. Also sensory 
fibres, which convey the sensations of pain, as 
in angina pectoris. 

(c) The vagus supplies motor and sensory 
fibres to the soft palate, pharynx, oesophagus, 
and stomach. Stimulation of the central end of 
the cut vagus causes a reddening of the mucous 
membrane of the stomach. The vagus contains 
fibres which inhibit the vaso-motor centre, dilate 
the blood-vessels of the stomach, and cause the 
gastric juice to be poured out. 

Effects of dividing the Vagi. — If the vagi 
he divided in the neck of a rabbit or dog, the 
following phenomena will be noticed : 

(1.) The number of respirations per minute 
will fall to one-third their normal number, but 
each respiration is about five times as deep, so 
that the quantity of air entering the chest is not 
altered. The vocal cords are apt to fall together 
from paralysis of the muscles of the larynx. 



MEMORANDA OF PHYSIOLOGY. 253 

Foreign bodies, as food ingested and mucus, are 
liable to accumulate in the air-passages. 

(2.) The number of the contractions of the 
heart will be increased about twenty per cent., 
and in the dog at least there is increased arterial 
pressure. 

(3.) Food, if swallowed, accumulates in the 
oesophagus. Presence of food in the stomach 
no longer excites the secretion of gastric juice, 
though this latter effect is denied by some. 

(4.) The rabbit dies in twenty-four hours, the 
dog in a few days — death taking place from ac- 
cumulation of mucus or foreign bodies in the 
lungs and air-passages, often giving rise to 
pneumonia. 

Spinal Accessory. — This is purely a motor 
nerve, though it receives some sensory branches 
from the vagus. Its motor branches are dis- 
tributed to the trapezius and sterno- mastoid, 
and supply the vagus with motor nerves for the 
pharynx and larynx. 

Hypoglossal, or Ninth. — This nerve is purely 
motor, being distributed to hyo-glossus, genio- 
hyoid, genio-hyo-glossus, thyro-hyoid, and mus- 
cles of the tongue, and by its descending branch 
to the omo-hyoid, sterno-hyoid, and sterno- 
thyroid. 



254 MEMORANDA OF PHYSIOLOGY. 

THE SYMPATHETIC SYSTEM. 

The sympathetic system consists of numerous 
ganglia and nerves, which supply the viscera, 
glands, and blood-vessels of the body. The 
nerves consist both of medullated and non-me- 
dullated nerve-tubules ; the latter greatly pre- 
dominate. The sympathetic nerves are closely 
connected, and freely intermix with the cerebro- 
spinal nerves. There are numerous ganglia be- 
longing to the sympathetic system, and the 
nerves very frequently form plexuses, which for 
the most part surround blood-vessels, and are 
conducted by them to the viscera. 

The Cephalic portion of the sympathetic con- 
sists of four ganglia : 1. Ophthalmic. 2. Spheno- 
palatine, or Meckel's ganglion. 3. Otic, or 
Arnold's. 4. Submaxillary ganglion. 

The Cervical portion consists of three ganglia 
on each side of the neck, the superior, middle, 
and inferior. The superior ganglion is the largest 
of the three. It gives off several branches. Its 
superior branch is the direct continuation up- 
ward of the ganglion; it accompanies the in- 
ternal carotid into the skull, and divides into an 
outer and inner branch. The outer branch forms 
the carotid plexus, which lies on the outer side 
of the internal carotid, and communicates with 



MEMOEANDA OF PHYSIOLOGY. 255 

the Gasserian and Meckel's ganglia and the sixth 
nerve. The inner branch also accompanies the 
internal carotid, and forms the cavernous plexus; 
it communicates through the plexus with the 
third, fourth, fifth, and sixth nerves, and with 
the ophthalmic ganglion. Terminal filaments 
from these two plexuses accompany the branches 
of the internal carotid. The superior cervical 
ganglion also gives an inferior branch to the 
middle ganglion, external branches to cranial 
und spinal nerves, internal branches to pharynx, 
larynx, and heart (the latter being called the 
superior cardiac nerve), and anterior branches 
to the external carotid. The middle cervical 
ganglion communicates with the ganglia above 
and below, and gives spinal, thyroid, and car- 
diac branches. The inferior cervical ganglion 
communicates with the middle ganglion, gives 
branches which travel with the vertebral artery 
and form a plexus around it, also the inferior 
cardiac nerve. 

Cardiac Nerves — The superior, middle, and 
inferior cardiac nerves come from the cervical 
ganglia ; the middle is the largest. The deep 
cardiac plexus lies on the bifurcation of the 
trachea and behind the arch of the aorta, and is 
formed by the cardiac branches of the sympa- 
thetic and vagi. The superficial cardiac plexus 



256 MEMOKANDA OF PHYSIOLOGY. 

lies below the arch of the aorta and in front of 
the right pulmonary artery ; it helps to form the 
anterior coronary plexus. The posterior coro- 
nary plexus being formed by the deep cardiac 
plexus. 

The Thoracic Sympathetic consists of a 
series of ganglia, placed on each side of the 
spine, resting against the heads of the ribs. The 
external branches of the ganglia communicate 
with the dorsal spinal nerves. The internal 
branches of the upper six supply the aorta and 
pulmonary plexus ; the internal branches of the 
lower six unite to form the three splanchnic 
nerves. The great splanchnic is formed by 
branches from sixth to tenth ; it perforates the 
diaphragm, and terminates in the semilunar 
ganglion and renal plexus. The lesser splanchnic 
is formed by tenth and eleventh ganglia, pierces 
the diaphragm, and enters the cceliac plexus. 
The smallest splanchnic comes from the last 
ganglion and passes to the renal plexus. The 
solar, or epigastric plexus, surrounds the cceliac 
axis, and sends branches forming plexuses, which 
surround the phrenic, gastric, hepatic, splenic, 
renal, superior and inferior mesenteric and 
spermatic arteries. The semilunar ganglia, 
which are situated on each side of the cceliac 
axis, are the largest ganglia of the body. 



MEMOKANDA OF PHYSIOLOGY. 257 

The Lumbar portion of the sympathetic con- 
sists of four ganglia connected by nerves. 

The Pelvic Sympathetic consists of four or 
five ganglia on each side. The Jiypogastriv plexus 
is situate between the common iliacs, and sup- 
plies branches through the inferior hypogastric 
plexus to the rectum, bladder, prostate, vagina, 
and uterus. Branches accompany the external 
iliacs to the lower extremities. 

Functions of the Sympathetic. — The centre 
of the sympathetic system is in the medulla ; 
section of the cord below the medulla causes a 
general dilatation of blood-vessels throughout 
the body. The ganglia take part in the reflex 
and automatic acts of the body ; such are the 
ganglia of the intestines and the ganglia situated 
in the heart. The non-striated muscles of the 
body, as the muscular fibres surrounding the 
blood- vessels, are supplied by the sympathetic. 

The Cervical Sympathetic contains : 

1. Yaso-motor fibres for the corresponding 
side of the head. 

2. Fibres which supply the dilating muscular 
fibres of the iris. 

3. Accelerating fibres for the heart. 

4. Fibres for the salivary and lachrymal glands. 

5. Fibres proceeding to the medulla, which 
excite the inhibitory fibres of the vagu3. 

17 



258 MEMORANDA OF PHYSIOLOGY. 

6. Fibres to medulla, which stimulate the 
vaso-motor centre. 

The Thoracic Sympathetic gives off through 
the splanchnics : 

1. Vaso-motor fibres for the vessels of the 
viscera. 

2. Inhibitory fibres for intestine. 

3. Fibres inhibiting renal secretion. 

4. Fibres which inhibit the heart reflexly. 
The Abdominal and Pelvic Sympathetic 

contain fibres which are distributed to the ves- 
sels of this part ; but little is known of them ex- 
perimentally. 



I 



Section 15. 

THE SENSES. 

SMELL. 

The mucous membrane of the nose is sup- 
plied with branches of the olfactory nerve in 
the upper third of the nasal cavity ; branches of 
the second division of the fifth are distributed 
over the whole surface. The surface is in- 
creased by the turbinated bones, which are 
highly developed in some of the lower animals. 
The mucous membrane of the upper or olfac- 
tory region is provided with modified columnar 
cells, with which the terminations of the olfac- 
tory nerves are connected. 

Odoriferous substances give off minute par- 
ticles, which, when inhaled, come in contact 
with the epithelium of the olfactory tract, and 
excite the terminations of the olfactory nerve, 
giving rise to the sensations of smell. Oxygen 
seems necessary to the development of the sense 
of smell. 



260 MEMORANDA OF PHYSIOLOGY. 

Pungent odors, as of ammonia, are perceived 
by the fifth. 

TASTE. 

The tongue is the organ of taste. The mu- 
cous membrane of the tongue receives the im- 
pressions made upon it by the food, and these 
impressions are carried to the brain by special 
nerves. The papilla? lodge the terminations of 
the nerves and the taste-buds with which the 
nerves are connected. The nerves which, di- 
rectly or indirectly, administer to the sense of 
taste are the (1) glossopharyngeal supplied to 
the circumvallate papilla?, (2) lingual, to the 
front and sides of the tongue, and (3) chorda 
tympani. 

Special fu n ctioiis. 

H ' , _ , ( bitter tastes. 

1. Glossopharyngeal, ■( 

( savory tastes. 

( pungent tastes, acids, pepper, etc. 

2. Lingual, ■< sweet tastes. 

' common sensation. 

3. Chorda tympani, stimulates secretion of saliva. 

It is necessary for the development of taste 
that the substance should be in solution, one of 
the offices of the saliva being to dissolve sapid 
substances, and so render them more evident to 
the taste. 



MEMORANDA OF PHYSIOLOGY. 261 

FEELING AND TACTILE IMPRESSIONS. 

The skin contains special organs, as end-bulbs, 
touch-corpuscles, and also the termination of 
nerves, which, when stimulated by contact, ex- 
cite the sensations of touch. The afferent njerves 
are distributed to all parts of the surface of the 
body, and convey to the brain the sensations 
excited by contact. Sensations of touch may 
be divided into : 

(a) Sensations of pain. 

(b) Sensations of temperature. 

(c) Sensations of pressure. 

(d) Tactile judgments. 

(e) Muscular sense. 

It is probable there are separate nerves for 
conveying to the brain the different sensations 
of pain, temperature, etc. There is reason to 
believe that in the spinal cord, at least, the 
purely tactile sensations travel along special 
strands of nerves. 

SIGHT. 

THE EYE. 

Structure. — The eye has three tunics, or 
layers : 

(1) Sclerotic and cornea. 



262 MEMORANDA OF PHYSIOLOGY. 

(2) Choroid, iris, and ciliary processes. 

(3) Eetina. 

And three refracting media : 

(4) Aqueous humor. 

(5) Crystalline lens. 
(6)* Vitreous humor. 

(1.) The Sclerotic is a firm, dense, fibrous 
membrane, forming five-sixths of the external 
coat of the eyeball. It is composed of white 
fibrous tissue, and fine elastic fibres, with numer- 
ous connective -tissue corpuscles. It is continuous 
in front with the cornea, and is pierced behind 
by the optic nerve. It contains blood-vessels 
and nerves. 

The Cornea is transparent, and forms one- 
sixth part of the external tunic. It has five 
layers : 

(1) Epithelial cells of conjunctiva. 

(2) Anterior elastic lamina. 

(3) Cornea proper. 

(4) Posterior elastic lamina. 

(5) Layer of flattened cells lining anterior 
chamber. 

The cornea proper is continuous with the 
sclerotic, and consists of about sixty lamellae of 
transparent fibrous tissue, and numerous cor- 



MEMOKANDA OF PHYSIOLOGY. 263 

puscles contained in the cell-spaces. It is evas- 
cular, but contains nerves. 

(2.) The Choroid is a dark membrane lin- 
ing five-sixths of the eyeball, internal to the scle- 
rotic. Its external layer consists of veins — the 
vence vorticosce. Its middle layer consists of fine 
capillaries, and is called the tunica Ruychiana. 
The internal layer is formed of hexagonal cells, 
loaded with dark pigment-grannies. 

The Ciliary processes are formed by the 
plaiting and folding inwar 1 of the middle and 
internal layers of the choroid ; they are attached 
to the suspensory ligament in front, and are ar- 
ranged in a circle around the lens. 

The Iris is a circular contractile diaphragm 
in front of and touching the anterior surface of 
the lens. It is attached by its circumference to 
the cornea, sclerotic, and choroid, at their junc- 
tion with one another. Its inner edge forms 
the pupil. In structure it consists of muscular 
fibres, a fibrous stroma, and pigment-cells. The 
circular muscular fibres surround the pupil, the 
radiating fibres pass from the pupil to the cir- 
cumference. Arteries, long and anterior ciliary. 
Nerves, radiating fibres, sympathetic; circular, 
third nerve. 

The Ciliary Muscle consists of involuntary 
muscular fibres ; it arises at the junction of the 



264: MEMOKANDA OF PHYSIOLOGY. 

cornea and sclerotic, and is inserted into the 
choroid. When it contracts it pulls forward 
the ciliary processes and choroid, and relaxes 
the suspensory ligament. It is supplied by the 
third nerve. 

(3. ) The Retina forms the inner tunic of the 
eye, and contains the terminations of the optic 
nerve and certain minute bodies, the rods and 
cones, with which the optic nerve is connected. 
Its thickness varies from -^ to y o u m - ; it is 
thicker behind than in front, and contains eight 
layers, which from before backward are : 

(1) Nerve-fibres. (5) Outer molecular. 

(2) Nerve -cells. ' (6) Outer nuclear. 

(3) Inner molecular. (7) Rods and cones. 

(4) Inner nuclear. (8) Pigment-cells. 

The optic nerve passes through the retina and 
spreads out on its surface. External to this 
layer are the nerve -cells ; they are of pyrif orm 
shape and have numerous branches. The rods 
are of elongated form, the cones are shorter 
and thicker at their bases, the base being di- 
rected toward the lens. The fibres of Miiller 
pass directly through the layers and help to bind 
them together; 

[Some authors make ten layers. From the 
vitreous outward they are the following : 



MEMORANDA OF PHYSIOLOGY. 265 

1. The pigmentary layer. 

2. The membrana limitans interna. 

3. The expansion of the optic nerve. 

4. The ganglionic cell layer. 

5. The molecular layer. 

6. The internal granular layer. 

7. The intergranular layer. 

8. The external granular layer. 

9. The membrana limitans externa. 
10. The layer of rods and cones,] 

The Macula Lutea. — In the centre of the 
retina, and corresponding to the axis of the 
eye, is a yellow spot — the macula lutea ; it con- 
tains some yellow pigment, and is about ^jj in. 
in diameter. In its centre is a minute depres- 
sion, the fovea centralis. The rods are absent 
over the yellow spot, and the cones longer and 
narrower than elsewhere. The other layers are 
very thin over the fovea centralis. 

The Porus Opticus, or Optic Disc. — The 
optic nerve enters the retina about -^ in. on the 
inner side of the yellow spot. It appears as a 
round white disc, and is called the porus opti- 
cus. The arteria centralis retinm enters through 
its centre. The rods and cones are not present 
over the porus opticus. 

(4.) The Aqueous Humor. — The aqueous 



266 MEMORANDA OF PHYSIOLOGY. 

fluid fills the space between the lens and cornea. 
*It closely resembles water, but contains a small 
quantity of salts dissolved in it. 

(5. ) The Lens is about £ in. in diameter, bi- 
convex, being more convex behind than in front, 
and is surrounded by a capsule. The outer 
portion of the lens is soft and easily detached, 
the succeeding layers are firmer, and the central 
part or nucleus is harder still. Faint white 
lines may be seen radiating from the centre to 
the circumference, which in the foetus are three 
in number and well-marked. In the hardened 
lens a succession of concentric laminae may be 
detached, like the coats of an onion. The la- 
minae are composed of fibres, their edges are 
finely serrated and fit into each other. The 
fibres are six-sided prisms, and are in reality 
elongated cells, and in the young state contain 
nuclei. 

Changes in the Lens by Age. — In the foztus 
the lens is nearly spherical. In the adult the 
anterior surface becomes more flattened than 
the posterior. In old age it becomes more flat- 
tened at both surfaces, and its transparency is 
impaired. 

(6.) The Vitreous Humor. — The vitreous 
body occupies the chamber between the lens and 
the retina. It is of a gelatinous consistence, and 



MEMORANDA OP PHYSIOLOGY. 267 

forms a support for the retina. When hardened 
it exhibits a laminated structure, and numerous 
corpuscles scattered through it. 



ACCOMMODATION. 

If a convex lens be made to throw the image 
of an object upon a screen, and then the object 
move farther away or nearer to the lens, the 
image on the screen will be indistinct, being out 
of focus, and the lens must be moved to get a 
distinct image. In a similar manner, the crys- 
talline lens must be moved, or its convexity al- 
tered, when viewing objects at different dis- 
tances, in order to obtain distinct images on the 
retina. If distant objects are being looked at, 
objects a foot distant will be indistinct, and vice 
versa, unless some accommodating mechanism 
exists. This is accomplished, not i>y moving the 
lens, as in a telescope, but by altering its con- 
vexity. The lens is more or less elastic, and its 
anterior surface is kept flattened by the tension 
of the elastic suspensory ligament. If the sus- 
pensory ligament is relaxed, the lens becomes 
more convex, and when the suspensory ligament 
tightens it flattens the lens again. The con- 
traction of the ciliary muscle, by drawing for- 



268 MEMOEANDA OF PHYSIOLOGY. 

ward the ciliary processes, relaxes the suspensory 
ligament, and therefore the lens becomes more 
convex. 

The accommodation of the eye for near ob- 
jects is a muscular act, being effected by the 
contraction of the ciliary muscle, the lens be- 
coming more convex ; accommodation for dis- 
tant objects is simply effected by the elasticity 
of the suspensory ligament, the ciliary muscle 
relaxing and the lens becoming natter. Images 
of distant objects are thrown upon the retina 
when the ciliary muscle is not contracting, 
images of near objects are thrown behind, and 
the lens must be rendered more convex, in order 
to bring them to a focus on the retina. 

[Emmetropia. — In the emmetropic eye the 
parallel rays are brought to a focus upon the 
retina when the eye is at rest. It is the normal 
eye.] 

Hypermettopia. — In the hypermetropic eye, 
the horizontal axis of the eye is shortened, so 
that the retina is nearer the lens than in the 
normal eye. The images of objects are formed 
behind the retina ; those of distant objects can 
be brought to focus on the retina by contraction 
of the ciliary muscle, but the images of near 
objects are formed so far behind that no effort 
of the ciliary muscle will focus them on the ret- 



MEMORANDA OF PHYSIOLOGY. 269 

ina. Convex spectacles are used, especially for 
near objects. 

Myopia. — In the myopic eye the horizontal 
axis is elongated, so that the retina is farther 
away from the lens than in the normal eye. The 
image of objects will fall in front of the retina, 
especially the images of distant objects. The 
lens cannot be rendered sufficiently flat to bring 
them into focus, and concave glasses must be 
used. 

Presbyopia, or the long sight of old people, 
consists in a defective condition of the accom- 
modation apparatus, so that, while seeing distant 
objects distinctly, near ones are indistinct. 

Astigmatism. — It sometimes happens that 
the surfaces of the cornea are not equally con- 
vex, the cornea being more convex in the ver- 
tical meridian than in the horizontal, or vice 
versa. This will interfere with the distinctness 
of vision; most eyes are slightly astigmatic, 
with the greater curvature in the vertical me- 
ridian. 

Movements of the Pupil. 

The contraction of the pupil when light falls 
on the eye is a reflex act. The dilating fibres 
are supplied by the sympathetic, and the circu- 
lar by the third. The sympathetic is constantly 



270 MEMORANDA OF PHYSIOLOGY. 

in action, so that when the stimulus of light is 
removed the pupil dilates. 

The circular fibres contract, and overcome the 
contraction of the radiating, when stimulated 
by light or during sleep. Division of the sym- 
pathetic in the neck of the rabbit causes con- 
traction of the pupiL 

The pupil contracts : 

(1) When stimulated by light. 

(2) When we accommodate for near objects. 

(3) When the eyeball is turned inward. 

(4) Through the action of certain drugs— 
opium, calabar bean. 

The pupil dilates ; 

(1) When the stimulus of light is removed. 

(2) When the eye accommodates for distant 
objects. 

(3) Through the action of certain drugs, as 
belladonna {sulphate of atropia). 

(4) In dyspnoea. 

Functions of the Retina. 

The retina receives the images of objects, and 
through its agency they are perceived by the 
mind. The exact use of the different layers of 
the retina is unknown, but the perception of 



MEMORANDA OF PHYSIOLOGY. 271 

light is probably due to the rods and cones. 
The power of distinguishing color is said to be 
due to the cones. 

The optic nerve enters the retina -fa in. to the 
inner side of the yellow spot, and when viewed 
from the front by means of an ophthalmoscope, 
it appears like a round, white spot termed the 
optic disc. The optic disc is insensitive to light. 
This can be demonstrated by fixing the right 
eye (the left being closed) on a dark spot on a 
sheet of paper held 10 in. from the eye. If a 
black point, like the tip of a pen, be made to 
move from right to left toward this spot, it be- 
comes invisible when it reaches a point 2-J- in. 
from it, but will reappear again on moving 
nearer. The image of the spot is projected on 
to the macula lutea in the centre of the retina, 
and the image of the moving point falls on the 
optic disc (tV in. from yellow spot) when 2-J- in. 
from the fixed black spot. This shows that the 
optic disc is insensitive to light. 

. The macula lutea occupies the centre of the 
retina, and is the most sensitive part of it. 
Small objects appear more distinct when their 
images fall on the centre of the retina, as when 
we look straight at an object. Points which ap- 
pear separate when their images fall on the yel- 
low spot, appear as only one when their image 



272 MEMORANDA OF PHYSIOLOGY. 

falls elsewhere, as when they are moved out of 
the centre of the field. 

Purkinjtfs Figures. — If a strong ray of light 
be concentrated on the edge of the sclerotic near 
the cornea, the light will pass through the scle- 
rotic and throw the shadow of the retinal ves- 
sels on the retina, a dark, branching figure being 
seen. Or if, on entering a dark room, a candle 
is moved up and down by the side of the eye, 
the same appearance will be seen. As the ves- 
sels lie in front of the rods and cones, it is 
probable that it is through them that light is 
perceived. 

HEAKING. 

THE EAR. 

The organ of hearing is divided into : 

(1) External ear. 

(2) Middle ear or tympanum. 

(3) Internal ear or labyrinth. 

(1.) The External ear consists of the pinna 
and the external auditory canal. The pinna 
consists of an irregularly concave piece of yellow 
elastic cartilage, which receives the sound and 
conducts it to the meatus. The external audi- 
tory canal is 1J in. in length, partly cartilaginous 



MEMORANDA OF PHYSIOLOGY. 273 

and partly bony, and conveys the vibrations of 
so and to the membrana tympani, which closes 
its inner end. 

(2.) The Tympanum is a small cavity hol- 
lowed out of the temporal bone, which com- 
municates with the external air through the 
Eustachian tube, and contains a chain of bones 
which convey vibrations received by the mem- 
brana tympani to the fluids surrounding the 
nervous mechanism of the internal ear. Its 
roof is formed by a thin plate of bone, which 
separates it from the cranial cavity. The floor 
is narrow and corresponds to the jugular fossa 
beneath. Its anterior wall corresponds with the 
carotid canal, and presents the canal for the 
tensor tympani and the opening of the Eusta- 
chian tube. The posterior wall presents the 
openings of the mastoid cells. The outer toall is 
occupied by the membrana tympani, and near 
its margin are three small apertures, the iter 
chordm posterius and iter clwrdce anterius for 
the entrance and exit of chorda tympani, and 
the Glaserian fissure for the handle of the 
malleus, laxator tympani, and some tympanic 
vessels. 

The membrana tympani is a thin, transparent 
membrane, which forms the outer wall of the 
tympanic cavity ; it is of oval form, and placed 
18 



274: MEMOKAISDA OF PHYSIOLOGY. 

obliquely, so that its outer surface looks down- 
ward and somewhat forward. The handle of 
the malleus is attached to its inner surface, and 
draws the membrane inward, so that its outer 
surface is concave. 

The inner wall presents the — 

1. Fenestra ovalis. 

2. Fenestra rotunda. 

3. Promontory. 

4. Kidge of the aquaeductus Fallopii. 

5. Pyramid. 

6. Opening for the stapedius. 

The fenestra ovalis communicates with the 
vestibule, and is closed by a membrane to which 
the base of the stapes is attached. The fenes- 
tra rotunda, placed below and behind, opens 
into the cochlea, but is closed by a membrane 
in the recent state. The promontory corresponds 
with the first turn of the cochlea. The pyramid 
is a conical projection which transmits the sta- 
pedius muscle through the minute canal in its 
centre. 

The ossicles of the tympanum consist of the 
malleus, incus, and stapes. 

The malleus consists of a head, a neck, and 
three processes. The incus resembles a bicus- 
pid tooth, and consists of a body and two pro- 



MEMOKANDA OF PHYSIOLOGY. 275 

P 

cesses. The stapes resembles a stirrup. The mus- 
cles of the tympanum are the tensor tympani, 
which arises from the petrous portion of the 
temporal bone and the walls of its canal ; it is 
reflected around the processus cochlearif ormis, 
and is inserted into the root of the handle of 
the malleus. The laxator tympani arises from 
the spine of the sphenoid, passes through the 
Glaserian fissure, and is inserted into the neck 
of the malleus. This muscle is considered by- 
some to be a ligament. The stapedius arises 
from the walls of its canal, and is inserted into 
the neck of the stapes. 

(3. ) The Internal Ear or Labyrinth consists 
of the vestibule, semicircular canals, and coch- 
lea. 

The Vestibule is situated on the inner side of 
the tympanum, behind the cochlea, and in front 
of the semicircular canals. It is somewhat ovoid 
in shape, and measures about £ in. in length. 
On its outer wall is the fenestra ovalis, closed 
by the base of' the stapes and membrane ; on 
its inner wall is the fovea hemispherical pierced 
by minute holes, for the filaments of the audi- 
tory nerve and opening of the aquaeductus ves- 
tibuli; on its roof is a small depression, the 
fovea semi-elliptica, and behind are the five 
openings of the semicircular canals, and in 



276 MEMOBANDA OF PHYSIOLOGY. 

front an opening which communicates with the 
cochlea. 

The Semicircular Canals are three bony 
canals of about -£$ in. in breadth, which open 
into the vestibule, on its posterior aspect, by 
five openings, the superior and posterior having 
one opening in common. 

The superior is vertical and transverse in po- 
sition. 

The posterior is vertical and longitudinal. 

The external is horizontal. 

The Cochlea is situated in front ef the ves- 
tibule, and resembles a small snail-shell. It is 
i in. in length, and consists of a canal which 
winds spirally around a central column. This 
osseous canal is 1-J in. in length, and winds 2-J 
times around the central axis or modiolus. The 
canal is divided into two by a delicate plate of 
bone, the lamina spiralis, which follows its 
windings. From the edge of the lamina spiralis 
two membranous structures stretch to the outer 
wall, dividing it into three canals. The mem- 
branes are called the M. of Eeissner and the M. 
of Corti, or membrana basilaris. The canals are 
the scala vestibuli, scala tympani, and scala 
media or canal of Con*ti, the latter interposed 
between the other two. The scala media con- 
tains the organ of Corti. The scala tympani 



MEMORANDA OF PHYSIOLOGY. 277 

communicates with the tympanum by means of 
the foramen rotunduin, the scala vestibuli with 
the vestibule, though both openings are closed 
by a membrane in the recent state. 

The membranous labyrinth is a closed mem- 
branous sac containing fluid. It corresponds in 
shape to the vestibule and semicircular canals, 
and is continuous with the canal of Corti ; it 
contains the terminations of the auditory nerve, 
is filled with the endolymph, and surrounded by 
the perilymph. The vestibular portion consists 
of two sacs: the utricle, lodged in the fovea 
hemi-elliptica, and the saccule in the fovea hemi- 
spherica. The membranous semicircular canals 
are about one-third the diameter of the osseous 
canals ; they are hollow, and open into the utri- 
cle. In the endolymph of the utricle, saccule, 
and ampullae of the semicircular canals there 
are hair-like processes attached to the epithelial 
cells, and numerous crystals of carbonate of lime 
called ooliths. 

The membranous cochlea consists of the S. 
vestibuli and S. tympani, containing perilymph, 
and the canal of Corti, containing the endo- 
lymph and organ of Corti. 

The organ of Corti is situated on the mem- 
brana basilaris, and consists of rods of Corti, and 
numerous hair-cells. The rods of Corti are 



278 MEMOKANDA OF PHYSIOLOGY. 

arranged in rows, their upper ends in contact 
with one another, and their lower ends rest- 
ing on the membrana basilaris. The hair-ceils 
are supported on the rods, and consist of col- 
umnar epithelium provided with hair-like pro- 
cesses. 

The Auditory Nerve is distributed to the 
vestibule and cochlea. The vestibular division 
divides into five branches, which are distributed 
to the utricle, the saccule, and the three am- 
pullae of the semicircular canals. The termina- 
tions of the nerves are connected with the hair- 
cells and float in the endolymph. The cochlear 
division passes into a small, bony canal, which 
runs up the modiolus, and then is distributed to 
the rods of Corti, and hair-cells passing between 
the layers of the lamina spiralis. 

Functions of the External and Internal 
Ear. — The external ear collects the waves of 
sound, and the auditory canal conveys them to 
the membrana tympani. 

The membrana tympani receives the waves, 
and is set into vibrations accordingly. 

The tensor tympani renders tense the mem- 
brana tympani. When the membrane is tense 
it readily responds to high sounds, and when 
relaxed it is best adapted for receiving low 
sounds. 



MEMORANDA OF PHYSIOLOGY. 279 

The auditory ossicles. — The malleus is attached 
by its handle to the membrana tympani, and 
any movement of the latter is communicated 
to the malleus. The incus and stapes trans- 
mit the vibrations to the membrane covering 
the fenestra ovalis, and the vibrating mem- 
brane sets in motion the perilymph of the ves- 
tibule. 

The stapedius regulates the action of the 
stapes. 

The Eustachian tube forms a communication 
between the tympanum and external air, and 
is opened during the act of swallowing. 

The labyrinth. — The vibrations communicated 
by the ossicles to the perilymph of the vestibule 
pass through the cochlea, ascending by the 
scala vestibuli, and descending by the scala tym- 
pani to the fenestra rotunda, and also passing 
along the perilymph of the semicircular canals. 
The vibrations of the perilymph are communi- 
cated to the endolymph of the scala media, and 
the terminations of the auditory nerve by means 
of the rods of Corti and hair-cells. The endo- 
lymph contained in the membranous labyrinth 
of the vestibule and semicircular canals in like 
manner communicates the vibrations to the 
auditory nerve through the medium of the hair- 
cells. 



280 



MEMORANDA OF PHYSIOLOGY, 



The vibrations travel along the following 
channels to reach the auditory nerve : 
Concha. 

External auditory meatus. 
Membrana tyrnpani. 
Ossicles. 



Perilymph of Vestibule— Utricle and Saccule. 



Perilymph of S. vestibuli. 

Pe ' Trr, nph o* S. tyrnani. 
Kna !»•■ ra».->- . C. '» »>rti. 



] Perilymph of semicircular 

canals. 
I Enr.olympTi of ampuIlsB. 

I (j.- lt ti:s an:; liair-v^.is. 



Hair-cells. 
Auditory nerve. 



. \ditc: ,T 'ierv? 



Sertion 16. 

MECHANISM OF SPEECH. 

Speech constitutes one of the great different 
ces between man and the lower animals, and is 
of great importance as a means of communica- 
tion between man and hia fellows. It depends : 

11. U{:gi* a -uitablo mechanical apparatus for 
the production of sounds. 

2. Other mechanical arrangements in the 
oral cavity for modifying those sounds. 

3. Nervous centres for co-ordinating the 
muscular movements, and intellectual powers 
of a high order to express ideas in language. 

I. THE LARYNX. 

The larynx consists of cartilages, various 
muscles and ligaments. 

1. The Cricoid resembles a signet-ring, 
being deep behind and narrow in front. It 
gives attachment at its front and sides to the 
crico-thyroid, and behind this to the inferior 
constrictor. Posteriorly it gives attachment to 



282 MEMOBANDA OF PHYSIOLOGY. 

the oesophagus and crico-arytenoideus posticus. 
Its upper border gives attachment to the crico- 
thyroid membrane and crico-arytenoideus late- 
ralis. It has articular surfaces, for the thy- 
roid behind, and arytenoids superiorly. 

2. The Thyroid cartilage consists of two lat- 
eral halves, of a quadrilateral shape, joining at 
an acute angle in front, and forming at their 
upper angle the pomum Adarni. The outer sur- 
face gives attachment to the thyro-hyoid, ster- 
no- thyroid, and inferior constrictor. At the 
posterior inferior angle there are two cornua for 
articulation with the cricoid. Its posterior bor- 
der gives attachment to the stylo-pharyngeus. 
At the angle formed by the alas on the inner 
aspect it gives attachment to the epiglottis, and 
false and true vocal cords, and thyro-aryte- 
noidei. Its inferior border gives attachment to 
the crico-thyroid. 

3. The Arytenoid cartilages resemble pyra- 
mids, having three surfaces, a base, and apex. 
The base is seated on the cricoid, its anterior 
angle giving attachment to the true vocal cords, 
and its external angle to the crico-arytenoid, 
posticus, and lateralis. The posterior surface 
gives attachment to the arytenoids, and the an- 
terior to the false vocal cords and thyroaryte- 
noids. 



MEMORANDA OF PHYSIOLOGY. 283 

4. The Epiglottis is shaped like an obovate 
leaf, being round at its free extremity, and 
pointed inferiorly where it is attached to the 
angle formed by the alas of the thyroid. 

It is composed of yellow elastic cartilage, and 
covers the superior opening of the larynx, and 
is covered by mucous membrane, which is re- 
flected to the neighboring parts. 

5. The Oornicula Laryngis, or Cartilages 
of Santorini, are two small nodules of yellow 
fibro-cartilage, which are placed at the summit 
of the arytenoids. 

5. The Cuneiform Cartilages, or Cartilages 
of Wrisberg, are two yellowish cartilaginous 
bodies situated in the aryteno-epiglottidean 
folds. 

Structure of Hie cartilages. — The epiglottis, 
cornicula laryngis, and cuneiform cartilages, 
consist of yellow fibro-cartilage. The other 
cartilages are hyaline, resembling the costal, 
and are prone to ossify. 

The Vocal Cords— so-called from their being 
concerned in the production of the voice — are 
two bands of yellow elastic tissue covered with 
mucous membrane, attached in front to the 
angle between the alee of the thyroid and 
behind to the anterior angle of the base of the 
arytenoid. They are continuous below with 



284 MEMOEANDA OF PHYSIOLOGY. 

the crico-thyroid membrane, and their free 
edges are directed upward. 

The False Vocal Cords are two folds of mu- 
cous membrane, enclosing fibrous tissue, situa- 
ted above the true vocal cords. 

The Ventricle of the Larynx is a fossa be- 
tween the true and false vocal cords ; it com- 
municates with the sacculus laryngis, and 
forms a pouch between the superior, or false 
vocal cords, and the thyroid cartilage. 

The Rima Glottidis is the narrow fissure be- 
tween the inferior- and true vocal cords. In the 
male it measures eleven lines, and its breadth 
is from three lines to half an inch. In the fe- 
male, and in the male below puberty, it is eight 
lines in length and two lines in breadth. When 
a sound is produced its edges are approximated. 

Action of the Muscles. — The crico-thyroids 
tighten the vocal cords by pulling the anterior 
part of the thyroid downward. The thyro-ary- 
tenoids have an opposite effect. The crico-ary- 
tenoid later ales, by pulling forward the outer 
angle of the arytenoid cartilages, will approxi- 
mate the vocal cords. The posterior crico-ary- 
tenoids pull back the outer angle of the arytenoid 
cartilages, and separate the vocal cords. 

The arytenoids, by pulling the arytenoids 
nearer together, approximate the vocal cords. 



MEMORANDA OF PHYSIOLOGY. 285 

Different Characters of Voice. 

1. Loudness or Intensity depends upon the 
amplitude of the movements of the cords, and 
hence, upon the force of the expiratory blast. 

2. Pitch depends upon the rate of the vibra- 
tions. The number of vibrations being depen- 
dent upon the tension and length of the cords, 
the tenser the cords the higher the pitch ; the 
shorter the cords the higher the pitch. When 
a high note is being made, the cords are approx- 
imated ; when a low note, they are separated. 
It is said that no sound is elicited if they are 
separated more than one- tenth or one-twelfth 
of an inch. Males have longer cords than fe- 
males and children, and hence have a lower 
range of notes. But every voice has a certain 
range, in consequence of the power possessed 
by each individual to vary the tension of the 
cords. The following table will exhibit the ac- 
tions of the muscles in altering the pitch : 



Govern Pitch of the Voice. 

f j crico-thyroids ) depress front of thyroid 
| ( sterno-tDyroids J and stretch v. cds. 
Raise pitch-! 

I \ %S£fiT* ^ [approbate V ' ^ 

f j thyro-arytenoids } elevate thyroid and 
Lower pitch-! 1 thyrohyoids f relax v. cds. 

[ crico-ary. post. open glottis. 



286 MEMOBANDA OF PHYSIOLOGY. 

3. Quality of the voice depends chiefly upon 
individual peculiarities. 

Nerve-supply. — The chief muscle which 
makes tense the vocal cords — the crico-tbyroid 
— is supplied by the superior laryngeal ; the rest 
of the intrinsic muscles by the recurrent laryn- 
geal. 

Movements during Respiration. — During in- 
spiration the rima glottidis opens widely, and is 
in a semi-contracted state during expiration. 

It is closed entirely prior to a cough or sneeze. 

The Larynx as a Musical Instrument. — 
The different kinds of musical instruments are 
strings, flutes, and reeds. In certain instru- 
ments, as the harp, the musical sounds are pro- 
duced by vibrating strings, but no strings as short 
as the vocal cords could give a tone comparable 
to the human voice. In the flute-pipes, the 
sound is produced by the vibration of an elastic 
column of air. Possibly this is the case with 
.the notes of birds, but it would require a column 
of six feet to produce the ordinary bass voice. 
In the reed, the sound is produced by the vibra- 
tions of certain tongues, as in the accordeon, 
harmonium, etc. With this kind of instrument 
the human larynx agrees, the notes being pro- 
duced by the vibrations of the vocal cords, the 
pitch depending on their length and tension. 



MEMORANDA OF PHYSIOLOGY. 287 

II. ARTICULATE SOUNDS. 

The larynx produces tones only, but speech 
consists in the modification of the laryngeal 
tones, so as to produce articulate sounds. 

Vocal Sounds. — The only true vocal sounds 
are the vowels ; the consonants are sounds pro- 
duced, not by the vocal cords, but by the ex- 
piratory blast being modified in the mouth and 
throat. 

The vowel-sounds are produced in the larynx, 
but are modified in their passage through the 
pharynx and mouth. Thus, in pronouncing the 
letters oo the lips are protruded and the larynx 
is depressed, making the column of air as long 
as possible. With the sound ee the lips are re- 
tracted and the larynx raised, making the col- 
umn of air as short as possible. 

Consonants are sounds produced in the buccal 
cavity. The labials are produced by approxi- 
mation of the lips. The dentals by the approxi? 
mation of the tongue to the teeth or hard pal- 
ate. The gutturals by the approximation of the 
root of the tongue to the soft palate. Other 
varieties, as explosives, aspirates, and resonants, 
are formed by a rush of air through the lips or 
teeth, or causing the nasal chamber to act as a 
resounding cavity. 



0«tton 17. 

OEGANS OF GENEEATION. 

UTERUS. 

The Uterus is a hollow, muscular, pear- 
shaped organ, with thick walls, situated in the 
pelvic cavity. It is flattened from before back- 
ward, about 3 in. long, and 7 to 12 drs. in 
weight. It consists of a fundus, a body, and 
cervix. The fundus is rounded, and is directed 
upward and forward. The cervix projects into 
the vagina, and opens into it by means of a 
transverse fissure, the os uteri. The cavity is 
of triangular shape in its upper part, the base 
being toward the fundus, where the Fallopian 
tubes enter ; the inferior angle is constricted 
and forms the internal os, which opens into the 
cavifcy of the cervix. The cavity of the cervix 
is somewhat spindle-shaped, being constricted at 
the internal and external orifices. 

Structure. — The uterus consists of serous, 



MEMOKANDA OF PHYSIOLOGY. 289 

muscular, and mucous coats. The serous layer 
passes from the rectum on to the upper part of 
the vagina, then upward, covering the whole of 
the posterior wall of the uterus ; it is reflected 
over the fundus and covers only three-fourths 
of the anterior surface, and passes on to the 
bladder. Two folds, which connect the sides of 
the uterus with the walls of the pelvis, form 
the broad ligaments, and contain the Fallopian 
tubes and ovaries. 

The muscular coat consists of external, mid- 
dle, and internal layers, of which the latter is 
the thickest : it forms concentric rings around 
the entrance of the Fallopian tubes and around 
the cervix. 

The mucous memh % ane lining the cavity of the 
uterus is smooth and soft, and of a dull red 
color, and contains numerous tubular glands. 

The membrane of the cervix is thrown into 
numerous rugse, and in the lower part there are 
some papillaa. The mucous membrane is lined 
throughout with ciliated columnar epithelium, 
except at the cervix, where it is flattened and 
non-ciliated. 

The Fallopian Tubes are contained in the 

broad ligament, and are between 3 and 4 in. in 

length. At their inner end they communicate 

with the cavity of the uterus : they enlarge as 

19 



290 MEMORANDA OF PHYSIOLOGY. 

they proceed outward, and end in numerous 
processes termed fifnbrim, one of which is at- 
tached to the ovary. These fimbrise are ar- 
ranged in a radiating" manner around the ab- 
dominal opening of the tube. The tube itself 
consists of a serous, muscular, and mucous coat. 
The muscular contains longitudinal and circular 
fibres, and the mucous membrane is lined by 
columnar ciliated epithelium. 

OVARIES. 

The ovaries are small bodies about 1J in. in 
length ; they weigh from 1 dr. to 1-J- drs. each, 
and are enclosed between the layers of the 
broad ligament. They are for the most part 
enclosed by the posterior, and touch the an- 
terior layer at their anterior border ; along this 
line is the hilus, where the vessels enter. 

Structure. — The ovary is surrounded by a firm, 
fibrous capsule, which is not so firm or dense as 
the tunica albuginea of the testis. The sub- 
stance of the ovary consists of a stroma com- 
posed of connective tissue, and a few muscular 
fibre cells and blood-vessels. In this stroma the 
Graafian follicles are imbedded. 

The Graafian Follicles consist of small vesi- 
cles, which are scattered in great numbers 



MEMORANDA OF PHYSIOLOGY. 291 

through the ovary. The smallest measure about 
T ^7 in., and lie in the cortical part. The me- 
dium-sized follicles occupy the more central 
parts, and are about ^o in. diameter, and are 
few in number. The largest of all, only few in 
number, lie near the surface, and project from 
it. The mature follicles are surrounded by a 
fibrous and a vascular tunic, which have been 
called the membrana fibrosa and membrana ma- 
culosa. They are lined internally by several 
layers of columnar or rounded cells which form 
the membrana granulosa, in which the ovum 
is embedded, and that part of the membrana 
granulosa which surrounds it is termed the dis- 
cus proligerus. The vesicle is filled with a serous 
fluid called the liq. folliculi. 

The Oyum. — The ovum is a small, round body 
of y-Ju in. in diameter. It consists externally of — 

(1) Zona pellucida, or vitelline membrane. 

(2) Yelk, or vitellus. 

(3) Germinal vesicle. 

(4) Germinal spot. 

The zona pellucida is a fine, transparent mem- 
brane, often marked with fine, radiating lines. 
The yelk is a granular mass containing oil-glob- 
ules. The germinal vesicle is a clear spot situ- 

in. in 



292 MEMORANDA OF PHYSIOLOGY. 

diameter. The germinal spot is a dark, granular 
spot of about uoV u in. in diameter. 

Menstruation. — In the human female, from 
the ages of 14 to 45, menstruation takes place 
every month. The most important event du- 
ring this period is the escape of an ovum from 
the ovary. The uterus, Fallopian tube, and 
ov tries are congested, a Graafian follicle bursts, 
and the ovum is picked up by the fimbriated 
extremity of the Fallopian tube, and passed 
along toward the uterus. During this time the 
mucous membrane of the uterus becomes swol- 
len and congested, and a discharge of blood 
amounting to several ounces takes place from 
the uterus. It is probable, also, the mucous 
membrane of the uterus, including the glands, 
is discharged during this period. During the 
few days that menstruation is taking place, 
there is a feeling of lassitude, with pains in the 
back and loins. 

[The weight of evidence favors the belief 
that the uterine mucous membrane is not dis- 
charged at each menstrual period.] 

Corpus Luteum. — After the discharge of the 
ovum from the Graafian vesicle, there is an ef- 
fusion of blood into the ruptured follicle, the 
latter gradually disappears, and a sort of scar 
is formed. But the course of events is greatly 



MEMORANDA OF PHYSIOLOGY. 293 

influenced if pregnancy occur. If the ovum 
which was extruded becomes fertilized, certain 
changes take place : the cells of the membrana 
granulosa become hypertrophied, and a yellow, 
irregular body is formed, termed the corpus lu- 
teum. This body goes on enlarging for several 
months and is still of considerable size at par- 
turition, but shortly after it gradually dwindles 
away. If pregnancy do not occur, the ruptured 
follicle shrinks, and in a few. weeks is reduced 
to an insignificant scar. 

Impregnation. — The ovum, on entering the 
Fallopian tube, is passed onward by the action 
of the cilia. Its motion is slow, as it appears 
to spend several days in the Fallopian tube, 
though this is uncertain. If it meets with no 
spermatozoa, it dies and is discharged. But, if 
it becomes impregnated, certain changes imme- 
diately begin. 

Segmentation of the Ovum. — In the mam- 
mal the whole of the yelk at once takes part 
in the formation of the embryo, and its ovum is 
said to be Jwloblastic. In birds, only a part of 
the yelk at once takes part in the formation of 
the chick ; the rest provides a store of nutritive 
material for the embryo, and is termed the food- 
yelk. Such an ovum is meroblastic. The seg- 
mentation of the human embryo has never been 



294 MEMOKANDA OF PHYSIOLOGY. 

observed, but it is presumed to resemble that of 
other mammals, as the rabbit and dog. Shortly 
after the ovum has escaped from the G-raafian 
follicle the germinal vesicle disappears ; this 
takes place whether the ovum is fertilized or 
not. The ovum appears generally to meet with 
the spermatozoa in the Fallopian tube, and im- 
mediately after certain changes begin. 

The yelk, which consists of a granular mass 
of protoplasm, splits into two ovoid masses, and 
there appears in each a clear space, which re- 
sembles a nucleus. Then shortly each ovoid 
mass splits again, making four, each having a 
nuclear body. This division goes on, eight, six- 
teen, thirty- two segments making their appear- 
ance, until finally the granular yelk has become 
a mass of cells, each having a nucleus and cell- 
wall. 

In the next change the central parts become 
fluid, while a layer of cells accumulate at the 
circumference and form the blastoderm or blas- 
todermic membrane. This membrane at first 
divides into two, the epiblast and hypoblast, a 
third making its appearance in an intermediate 
position called the mesoblast. 

Chorion. — Meanwhile the zona pellucida has 
acquired a new character. It has become beset 
with numerous villi, giving the ovum a shaggy 



MEMOKANDA OF PHYSIOLOGY. 295 

appearance, and is now termed the chorion, and 
is probably derived from the cells of the epiblast. 
Shortly after the ovum has entered the uterus 
it consists of : 

1. Chorion covered with villi. 

C Epiblast. 

2. Blastoderm -< Mesoblast. 

( Hypoblast. 

3. Fluid granular contents. 

It is from the blastoderm that the fetal struc- 
tures are developed ; the different layers take 
the following part in the process. 

1. Epiblast. — Epidermis and appendages, 
great nervous centres, principal parts of the 
eye, ear, nose, and one layer of the amnion. 

2. Hypoblast. — Epithelial lining of the whole 
alimentary canal, and of the lungs, and one 
layer of the allantois. 

3. Mesoblast. — The bones, muscles, fasciae, 
peripheral nerves, vascular system, connective 
tissue, muscular coat of alimentary canal, outer 
layer of amnion, and part of allantois. 

Changes occurring in the Uterus. 

Prior to the entrance of the impregnated 
ovum into the uterus, certain changes occur in 



296 MEMORANDA OF PHYSIOLOGY. 

the character of its mucous membrane, in order 
to prepare a suitable bed for the reception of 
the ovum. These changes correspond to those 
which take place during the manstrual period. 
They consist easentially in a proliferation of the 
subepithelial cells, causing a thickening of the 
mucous membrane, enlargement and multipli- 
cation of the tubular glands, and hypertrophy 
of the blood-vessels. This thickened membrane 
is called the deeidua. Into this decidual mem- 
brane the ovum, on entering the uterus, becomes 
embedded, and into the enlarged glands, or spe- 
cially formed crypts, the villi of the chorion are 
received. The deeidua having enveloped the 
ovum, it becomes divided into three distinct 
parts, viz.: deeidua vera, deeidua reflexa, and 
deeidua serotina. The deeidua vera lines the 
general cavity of the uterus ; the deeidua reflexa 
is that part which covers the ovum ; the term 
deeidua serotina is applied to that portion of 
membrane which intervenes between the ovum 
and the uterine walls, and occupies the site of 
the future placenta. 

THE PLACENTA. 

During the first two or three weeks the 
ovum derives its nourishment through the evas- 



MEMORANDA OF PHYSIOLOGY. 297 

cular villi of the chorion, the latter taking up 
some of the albuminous matter with which it is 
surrounded. About the third or fourth week 
the villi contain delicate loops of capillary blood- 
vessels, which greatly assist in the absorption 
of nutriment material. At the end of the sixth 
to the eighth week (the ovum being about 1-^- 
iv. in diameter) the villi, which are embedded in 
the tissues of the decidua serotina, become 
larger and more complex, and there is a corre- 
sponding increase in the decidual membrane ; 
and in the course of another few weeks the pla- 
centa is completely developed, while the villi, 
which correspond to the decidua reflexa, un- 
dergo more or less complete atrophy. By the 
end of the eighth or ninth week the villi can 
still be separated from the maternal structures ; 
but, by the end of the third month or begin- 
ning of the fourth, they are so intimately con- 
nected that separation is no longer possible. 

The placenta has attained its full develop- 
ment by the end of the fourth month ; and 
when it has attained its full dimensions, toward 
the end of pregnancy, it is from seven to eight 
inches in diameter. 

Structure of placenta. — The placenta when 
fully formed consists of two portions, a fetal 
and maternal. The fetal portion consists of 



298 MEMORANDA OF PHYSIOLOGY. 

highly complex tufts of villi containing numer- 
ous loops of capillary blood-vessels. The mater- 
nal portion consists of numerous spaces or 
sinuses continuous with the blood-vessels of the 
mother, and which receive and surround the 
fetal villi. The villi dip into spaces filled with 
maternal blood. 

Circulation of the Blood. — The fetal blood 
is carried to the placenta by the two umbilical 
arteries; it then circulates through the villi 
and returns to the foetus through the umbilical 
vein. The blood is carried to the maternal 
portion by the uterine arteries, the blood enter- 
ing the sinuses through the so-called u curling 
arteries," and is returned by the uterine veins. 
There are no capillaries in the maternal por- 
tion, the blood entering the sinuses and return- 
ing by the veins. 

There is no direct blood-communication be- 
tween the mother and foetus, but the fetal 
villi. dip into the maternal blood in a way simi- 
lar to the intestinal villi, which dip into the 
contents of the intestine. 

Changes effected by the Placenta. 

The fetal blood gains nutrient material and 0. 
The fetal blood loses effete material (urea, 
etc.), and C0 2 . 



MEMORANDA OF PHYSIOLOGY. 29 J 

The maternal blood gains effete material and 
C0 2 . 

The maternal blood loses nutrient material 
and O. 

Structure of umbilical cord. — The umbilical 
cord when fully developed is from 18 to 20 
in. long. Externally it is invested by the am- 
nion, and contains the umbilical vein and two 
arteries embedded in a gelatinous material 
termed Wharton's jelly. Early in fetal life 
it contains the omphalo-mesenteric vessels 3 a 
second vein, the allantois, and umbilical duct. 

FETAL CIRCULATION. 

The arterial blood coming from the placenta 
to the foetus travels along the umbilical vein to 
the liver. After giving off several branches to 
the left lobe, it divides into two streams : the 
larger joining the portal vein and thus entering 
the liver ; the smaller passing directly into the 
inferior vena cava through the ductus venosus. 
In the inferior vena cava the blood carried by 
the hepatic veins and ductus venosus mixes with 
the blood which has circulated through the 
lower extremities. On entering the right auri- 
cle the blood of the inferior vena cava is directed 
by the Eustachian valve through the foramen 



300 MEMORANDA OF PHYSIOLOGY. 

ovale into the left auricle, and from thence into 
the left ventricle. The left ventricle forces it 
into the aorta, and it is then distributed to the 
head and upper extremities, a small quantity 
only passing into the descending- aorta. The 
blood which has circulated through the head 
and upper extremities returns to the heart along 
the superior vena cava, the blood then passing 
into the right ventricle and pulmonary artery. 
A small part of the blood in the pulmonary 
artery is conveyed to the lungs, but the major 
part passes through the ductus arteriosus into 
the aorta at the commencement of the descend- 
ing portion. This blood is distributed to the 
lower extremities, a certa'n portion of it enter- 
ing the hypogastric arteries and being conveyed 
to the placenta. 

Peculiarities of the Circulation in the Foe- 
tus. — The greater part of the blood of the um- 
bilical vein is submitted to the action of the 
liver, the liver being of large size during fetal 
life. The head receives the purest blood that 
enters the heart, viz. , that of the inferior vena 
cava, while the blood supplied to the lower 
extremities is that which has already circulated 
through the head and upper extremities. The 
great importance of the cephalic nervous centres 
makes it necessary for them to receive a large 



MEMOKANDA OF PHYSIOLOGY. 301 

amount of« arterial blood. It is probable that in 
early fetal life the two streams of blood passing 
through the right auricle are distinct. At a 
later period, as the foramen becomes smaller, 
it is possible that some mixture of the two 
streams may take place. 

Changes at Birth. — When the placental cir- 
culation ceases, and respiration through the 
lungs is established, an increased quantity of 
blood enters the lungs. 

The ductus arteriosus begins to contract soon 
after birth, and is completely closed from the 
fourth to the tenth day. 

The hypogastric arteries remain patent in 
their first part as the superior vesicle, but the 
portion between the bladder and umbilicus 
becomes obliterated from two to five days after 
birth, and remains as the anterior true ligament 
of the bladder. 

The ductus venosus and umbilical vein become 
obliterated a few days after birth : the ductus 
venosus can be traced as a fibrous cord in the 
fissure of the same name on the under surface 
of the liver, and the umbilical vein becomes the 
round ligament. 

The foramen ovale is closed by the tenth day, 
and the Eustachian valve is soon reduced to a 
trace. 



302 MEMORANDA OF PHYSIOLOGY. 



THE MAMMARY GLANDS. 

The mammary glands form two rounded 
eminences, which extend from the third to 
the sixth ribs. A little below their centre is the 
nipple, which corresponds in position with the 
fourth interspace. Around the nipple is the 
areola, which is of a darker color than the nip- 
ple itself. 

Structure. — The mammary glands consist of 
lobes connected together with fat and connec- 
tive tissue. The lobes consist of lobules, ducts, 
and blood-vessels. The ducts commence in 
small clusters of acini, which are lined by short 
columnar epithelium. The ducts empty them- 
selves into some fifteen or twenty excretory 
ducts termed galactophorous ducts, which con- 
verge to the areola, where they form dilatations 
termed the ampulla, which serve as reservoirs 
for the milk. The ducts become again con- 
tracted, and finally open on the summit of the 
nipple. The walls of the ducts consist of elas- 
tic tissue and muscular fibres, and are lined by 
columnar epithelium, except at their orifices, 
where it becomes squamous. 

Composition of Milk. — See page 133. 



MEMORANDA OF PHYSIOLOGY. 303 

THE TESTES. 

The testes occupy the scrotum : they are of 
an ovoid form, flattened from side to side, are 
about 1$ in. long, and weigh J oz. to 1 oz. 
Along the posterior border of the testis is situ- 
ated the epididymis, which is composed of the 
convolutions of the excretory duct of the 
testis : the upper part is called the globus major,' 
the lower part the globus minor. 

Structure. — The testes are surrounded by a 
fibrous capsule, the tunica albuginea, the sur- 
face of which is covered by the tunica vaginalis, 
except along the posterior border, where the 
vessels enter. The tunica albuginea passes into 
the substance of the gland, forming an incom- 
plete vertical septum, called the mediastinum 
testis. 

Minute Structure. — The testes consist of 
from two hundred and fifty to four hundred 
lobules: they are conical in shape, their bases 
being directed toward the circumference of the 
organ. The lobules are composed almost en- 
tirely of minute convoluted tubes, named the 
tubuii seminiferi. Each lobule contains several 
tubes, the total number having been calculated 
at eight hundred and forty, and their length 
2J- feet each. The diameter is ji-j to ^o u in* 



304 MEMOKANDA OF PHYSIOLOGY. 

They consist of a basement-membrane, and in 
the young subject are lined internally by cells 
resembling epithelium. In the adult a mass of 
cells may be seen, which are spermatozoa in 
various stages of development. 

The Vasa Recta. — At the apices of the lob- 
ules the tubuli become less convoluted, and 
unite together to form twenty or thirty larger 
ducts about ■£$ in., in diameter called the vasa 
recta. 

The Rete Testis. — The vasa recta enter the 
fibrous tissue of the mediastinum and form a 
net* work of tubes called the rete testis. 

The Vasa Efferentia consist of ten to twenty 
ducts, which emerge from the rete testis. They 
perforate the tunica albuginea. Their course 
is at first straight, but they become more and 
more convoluted as they proceed toward the 
epididymis, and form a series of small conical 
masses, the coni vasculosi. 

The Canal of the Epididymis. — The coni 
vasculosi empty themselves into a single duct, 
which by its numerous coils forms the globus 
major and globus minor, and then turns up- 
ward as the vas deferens. The canal is - 7 ] o to 
tjV in. in breadth, is lired by columnar cili- 
ated epithelium, and measures about 20 feet in 
length. 



MEMORANDA OF PHYSIOLOGY. 305 

The Vas Deferens is the excretory duct of 
the testis, and, commencing at the lower part 
of the globus minor, ascends as part of the 
spermatic cord to the internal abdominal ring ; 
it is continued to the base of the bladder, 
where, becoming enlarged and sacculated, it 
unites with the duct of the vesicula seminalis 
to form the common ejaculatory duct. 

It is about two feet in length, with a narrow 
canal and thick walls. 

/Structure. — 

1. External or connective -tissue coat. 

2. Muscular, two longitudinal, and interme- 
diate circular layer. 

3. Internal or mucous, arranged in longitudi- 
nal folds lined with columnar epithelium. 

Spermatozoa. — The spermatic corpuscles 
consist of a small oval body provided with a 
long, filiform tail. The body is about ^oW * n * 
in length, and the tail about 4-50 m - m length. 
The tail performs rapid vibratile movements, 
which enable the spermatozoa to find their way 
into the Fallopian tube, despite the action of 
the cilia. 

The spermatozoa are developed within the 
cells which line the tubuli seminiferi. The 
20 



306 MEMOKANDA OF PHYSIOLOGY. 

body and coiled-up tail may be seen inside some 
of these cells, from which the spermatozoon 
makes its escape. 

[This view concerning the development of 
the spermatozoa has given place to the belief 
that they are developed from the glandular 
epithelium cells of the tubuli semmiferi.] 



APPENDIX. 



Receipts and Losses of a Strong Man in 24 hours, 

{Pettenkofer and Voit.) 
Weight at commencement = 69.29 kilos. 
Weight at end =69.55 " 















^ 


Grammes in twenty- 
four hours. 


Water. 


C. 


H. 


N. 


0. 


•11 


Gains. 














Meat 139.7 


79.5 


31.3 


4.3 


8.5 


12.9 


3.2 


Albumin 41.5 32.2 


.0 


0.7 


1.55 


2.0 


0.3 


Bread 450.0 208.6 


109.6 


15.6 


5.77 


100.5 


9.9 


Milk 500.0 435 4 


35.2 


5.6 


3.15 


17.0 


3.6 


Beer 1025.0 961.2 


25.6 


4.3 


0.67 


30.6 


2.7 


Fat 70.0 1 .... 


53.5 


8.3 




81 




Butter 30.0 2.1 


22.0 


3.1 


0.03 


2.8 




Starch 7001 11.0 


26.1 


3.9 




29.0 




Sugar 17.0: 


7.2 


1.1 




8.7 




Salt 4 2 . ... 










4.2 


Water 286.3 286.3 












Inspired \ „ m n 
oxygen f • " • ' • ' uau 






224.0 




709.0 
1792.3 






2016.3= 




Sum of gains.. 3342.7 




315.5 


270.9 


19.47 


2712.9 


23.9 


Losses. 














Urine 1343.1 


1278.0 


12 60 


2.75 


17.35 


13.71 


18.1 


Faeces 114.5 


82.9 


14.50 


217 


2.12 


7.19 


5.9 


Expired pro- ^ 17 oq 7 
ducts. j lftSU 


828.0 


248.60 


243.22 


19.47 


663.10 
1946.20 






2189.5= 








275.70 


248.22 


2630.20 


24.0 


Difference, ) 














gains, mi- V . .145.3 




+39.8 


+22.7 


0. 


+82.7 


-0.11 


nus losses } 















308 APPENDIX. 

Metric System. 

One metre equals 39.87 English inches = 1 
yard 3.37 in. 

10 decimetres = 1 metre. 
100 centimetres = " 
1,000 millimetres = " 
One decimetre, or 10 centimetres, are nearly 
equal to 4 inches, and 25.4 millimetres equal an 
inch. 

One gramme =: 15.43 grains. 
10 decigrammes = 1 gramme. 
100 centigrammes = " 

1,000 milligrammes == " [lbs. 8oz. 

1,000 grammes = 1 kilogramme — 2 

One cubic centimetre of [grains Troy. 

distilled water weighs 1 gramme = 13.14 

1,000 cubic centimetres = 1 litre. [pints. 

1 litre - 35 fluid oz. = 2.113 

100 c.c. = Si " 

28.4 c.c. =1 " 

Thermometer Scales. 

1. Fahrenheit's scale, commonly in use in 
England, has its boiling-point at 212°, and 
freezing-point at 32°. 

2. Centigrade scale, in use on the Continent 



APPENDIX. 309 

of Europe, and universally in scientific works in 
England, has a boiling-point at 100°, and freez- 
ing at 0°. 

To reduce Fahrenheit to Centigrade, sub- 
tract 32 and multiply by 5 and divide by 9. 
C. = (F. - 32) x f. 

To reduce Centigrade to Fahrenheit, multiply 
by 9 and divide by 5, then add 32. F. = (C. x J) 
x32. 

[To reduce Centigrade to Fahrenheit, multi- 
ply by 1.8 and add 32.] 

Thus, to reduce 212° F. to C. 
C. = 212 - 32 x J. 
= 180 x f. 
= 100. 
Reduce 100 C. to F. 

F. = 100 x f [1.8] +32. 
= 180 + 32. 
= 212. 



INDEX. 



PAGE 

Absorption 174 

through the skin ... 55 
Accommodation of the 

eye 267 

Acid, carbonic, circum- 
stances affecting 
the excretion of.. 112 
carbonic, of the blood 65 

hippuric 6, 197 

lactic 7 

uric 4, 64, 197 

uric, murexide test 

for 5 

uric, Schiffs test for 5 

Acids, bile . . 164 

fatty, in perspiration 55 

Actions, reflex 226 

Adipose tissue 29 

Air, changes of, in res- 
piration 115 

complemental 110 

reserve 110 

residual 110 

tidal 110 

sacs, the 105 

Albumen 14, 16, 64 

acid 16 

Albuminates, quantity 
of, in different 
food 136 



PAGE 

Albuminoids 17 

Albuminous bodies 13 

Alkali albuminate 15 

Amyloids 131 

Animal heat 120 

Animals, cold-blooded.. 120 

warm-blooded 121 

Aphasia 245 

Apncea 113 

Appendix 307 

Aqueous humor, the 265 

Arterial pressure 80 

Arteries, the 69, 78 

bronchial, the 105 

contractility of 82 

innervation of the . . 89 

pulmonary, the 105 

Articulate sounds 287 

Asphyxia 114 

due to oxygen starva- 
tion 115 

| Astigmatism 269 

[ Automatic actions 225 

j Axis-cylinder 212 



Basal ganglia 242 

Bile 163 

secretion of 186 

acids of 164 



312 



INDEX. 



PAGE 

Bile pigments 163 

Biliprasin 163 

Bilirubin 164 

Biliverdin 164 

Blood, the 56 

amount of, in the 

body 68 

, changes in, in respi- 
ration 112 

circulation of, in the 

foetus 298 

coagulation of the ... 65 
fetal, changes effect- 
ed in by the pla- 
centa 298 

gases of the 63 

red corpuscles 57 

velocity of the flow 

of, in the arteries . 80 
white corpuscles. ... 61 

Bone 34 

Bronchi, the 102, 104 

Brunner's glands 162 



C alices of the kidney. . 192 
Capillaries, the 69, 83 

circulation in 84 

Carbohydrates 9, 131 

quantity of, in differ- 
ent foods 136 

Carbon in various foods 137 
Cardiac revolution, a . . , 75 
Cartilage 30 

fibro 32 

hyaline 31 

ossification in 37 

Casein 15 

Cells, hepatic 181 

Centres, cardiac, of the 

medulla 238 

respiratory, of the 
medulla 237 

vaso- motor, of the 
medulla 238 



Cerebellum, the 239 

functions of 241 

Cerebrin 7 

Cerebrum, the 244 

functions of the .... 245 
phenomena follow- 
ing removal of.. . 246 
motor and sensory 

paths of. 248 

Chemistry, physiological 1 
Chest, vital capacity of.. 110 

Cholesterin 7, 165 

Chondrin 18 

Chorion 294 

Choroid, the 263 

Chyle, the 98 

Ciliary muscle, the 263 

processes, the 263 

Circulation, the 69 

action of poisons on 

the 93 

effect of respiration 

on 118 

effects on, produced 
by muscular exer- 
cise 48 

fetal 299 

in asphyxia 114 

the, in capillaries. . . 84 
Coagulation of the blood 65 

Cochlea, the 276 

Cold-blooded animals. . . 120 
Conductivity, nervous.. 219 

Connective tissue 25 

Contractility, muscular. 44 
of the arteries. . . 82 
Contractions, Pfliiger's 

law of 222 

Corpora quadrigemina. . 239 

functions of 240 

Cornea, the 262 

Corpuscles, granular 62 

Malpighian, of the 

spleen 203 

red, of blood 57 



INDEX. 



313 



PAGE 

Corpuscles, red, of the 

blood, fate of 61 

red, of the blood, ori- 
gin of 01 

white, of blood 61 

Corpus luteum 292 

Corpus striatum 242 

Corti, organ of 277 

Coughing 117 

Crypts of Lieberktfhn. . . 162 



Defecation 170 

Deglutition 151 

Dentine 142 

Dermis 51 

Dextrin 12 

Dextrose 9 

Diabetes 185 

Diastase 172 

Diet for hard work 135 

for idleness 135 

normal 134 

Dietetics 133 

Digestion 139 

of fats 129 

of the stomach 158 

Digestive changes, sum- 
mary 171 

Ducts, biliary 181 

Dyspnoea 113 

Ear, the 272 

functions of the ex- 
ternal and inter- 
nal 228 

Elastin 19 

Electrical muscle - cur- 
rents '43 

Electrotonus 221 

Emmetropia 268 

Enamel 143 

End-bulbs of nerves 214 



PAGE 

Endocardial pressure... 77 

Endocardium 73 

Epiblast 295 

Epidermis 50 

Epididymis, the 303 

Epiglottis, the 283 

Epithelium 20 

ciliated 23,103 

columnar 22 

glandular 23 

tessellated or squa- 
mous 21 

transitional 22 

Eupncea 113 

Eustachian tube 279 

Excitability, nervous.. . 219 
Excretion of carbonic 

acid 112 

Expiration, forced 108 

Extra-cardiac centres. . '. 90 
Eye, the 261 



Facial, function of 250 

Fallopian tubes 289 

Fasciculi, muscular 40 

Fats 12, 129,177, 178 

action of pancreatic 
juice on 168 

destiny of 130 

in perspiration 55 

preparation for ab- 
sorption 175 

quantity, in different 

foods 136 

Fermentation test for 

grape-sugar 10 

Ferments 171 

in digestive fluids . . 172 

Fibrin 17, 67 

Fibrinogen 17, 67 

Fibro-cartilage 32 

Food 125 

nitrogenous 125 

Foods, the albuminous . . 174 



314 



INDEX. 



PAGE 

Ganglia, basal 242 

intrinsic cardiac 89 

of nervous system . 217 
Gases in the red blood- 
corpuscles 60 

of the blood 64 

Gastric juice 155 

secretion of 158 

Gelatin 18 

Gelatinous bodies 17 

Generation, organs of ... 288 

Gland, thyroid 206 

Glands, Br miner's 162 

the ductless 201 

lymphatic 96 

peptic 155 

Peyer's 162 

salivary 147 

salivary, innervation 

of 150 

sebaceous 54 

solitary 162 

sweat 52 

tubular, of the stom- 
ach 155 

Globulin 16, 60 

Glosso-pharyngeal, func- 
tion of 251 

Glycerine 12, 13 

Glycogen 11, 62, 1S2, 182 

Gmelin's test for bile 163 

Graafian follicles 290 

Grape-sugar 9 

Gray matter, of the ner- 
vous system, struc- 
ture of 216 

of the spinal cord. . . 229 

HiEMOGLOBIN 59 

Hair 53 

Hearing 272 

Heart, the 69, 70 

cavities of the 71 

innervation of the. . S9 



PAGE 

Heart, sounds of the .... 75 

valves of the 73 

Heat, animal 120 

gained and lost to the 

body 122 

production of, dur- 
ing muscular con- 
traction 46 

Hemispheres, cerebral. . 244 
cerebral, phenomena 
following removal 

of 246 

Hiccup 118 

Histology, physiological. 20 
Hoffman's test for tyro- 
sin 8 

Hydrocarbons. ... 12, 129 

Hypermetropia 268 

Hypoblast 295 

Hypoglossal, function of 253 
Hypoxanthin 6 

IMPKEGNATION 293 

Indican 198 

Inhibition, reflex 91 

Inhibitory action, of the 

vagus 90 

Inorganic materials 133 

Inosit 10 

Inspiration 106 

labored 107 

muscles of 107 

Intestine 169 

digestive changes in, 

summary of . . 173 

small structure of.. 160 

the large 169 

Intestines, movements of 170 

Invertin 172 

Iris, the 263 

contraction of 227 

Kidneys 188 

Krause's membrane 41 



INDEX, 



315 



PAGE 

Kreatin 6,64 

Kreatinin 6,64, 197 

Lacteals, what they ab- 
sorb 178 

Lactose 10 

Larynx, the 281 

action of the muscles 
of 284 

as a musical instru- 
ment 286 

Lecithin 7, 62 

Lens, crystalline, the 266 

Leucin 7 

Scherer's test for. . . 8 

Leucocytes 71 

Liq. sanguinis 63 

Liver, the 179 

action of, on albu- 
minous substance . 185 

functions of the 182 

functions of, in the 

foetus 186 

Lobules, hepatic 180 

Lungs, the 103 

Lymph, the 98 

movements of the . . . 100 

Lymphatic system 94 

Lymphoid tissue 2S 

Macula lutea, the 265 

Malpighian bodies, of 

the kidney 189 

corpuscles, of the 

spleen 203 

Mammary glands 302 

Mastication 146 

Meconium 187 

Medulla oblongata 234 

functions of 236 

nerve-centres in 237 

Membrane, ossification in 37 
Menstruation 292 



PAGE 

Mesoblast 395 

Metric system 308 

Milk, composition of ... . 133 
Millon's reaction for pro- 

teids 14 

Moore's test for grape- 
sugar 10 

Mouth, digestive changes 

in 171 

Mucin 18 

Murexide test for uric 

acid 5 

Muscle 39 

contractility of 44 

elasticity of 47 

non-striated 42 

currents 43 

Muscles of inspiration.. 107 
termination of 

nerves in 215 

Muscular exercise, effects 

of 48 

Muscular tissue 39 

properties of 42 

Myopia 269 

Myosin 17 

Nails 52 

Nerves 209 

accelerator 91 

afferent 224 

efferent 223 

cardiac 255 

cranial functions of 249 
electrical phenomena 

of 221 

functions and classi- 
fication of 223 

medullated 210 

non-medullated . ... 212 
properties and func- 
tions of..... 218 

sensory. ' 21 2 

Nerve-cells. 216 



316 



INDEX. 



PAGE 

Nerve-centres, functions 

of 225 

Nerve-current velocity . . 220 
Nervous mechanism, of 

respiration 115 

structure of the 209 

Nervous system 2US 

ganglia of 217 

gray matter, of the 

structure of 216 

white substance of 
the, structure of. . 216 

Neurilemma 211 

Neurin 7 

Neuroglia 217 

Nitrogen, in various 137 
foods of the blood . 65 
Nitrogenous bodies in 

perspiration 55 

Nceud, vital 116 

Nutrition 174 

of nerves 218 

Oculo-motoe, function 

of 249 

(Esophagus, the 153 

Olein 12, 13, 129 

Olfactory, function of . . . 249 
Optic nerve, function of 249 

Optic disc, the 265 

Optic thalamus, the .... 243 
Ossification, in cartilage 37 

in membrane 37 

Ovaries 290 

Ovum, the 291 

segmentation of . . . . 293 
Oxygen, of the blood 64 

starvation, a cause 
of asphyxia 115 

Pacinian bodies 214 

Palmatin 12, 13, 129 

Pancreas, the 166 

Pancreatic juice 166 



PAGE 

Paraglobulin. . .17, 60, 64, 67 

Pepsin 172 

Peptones 17, 177, 178 

Periaxial space 211 

Pericardium, the 70 

Perspiration 54 

Perivascular space 95 

Pettenkof er's test 164 

Peyer's glands 162 

Pfluger's law of contrac- 
tion 222 

Physiological chemistry. 1 

histology 20 

Pigment 25 

Pigments, urinary 198 

Piria\s test for tyrosin. . 9 
Placenta, the 296 

changes in the blood 

effected by 298 

Plexuses, sensory 213 

Pneumogastric function 

of 251 

Poisons, action of on the 

circulation 93 

Presbyopia 269 

Pressure, arterial SO 

endocardial 77 

Proteids 13 

action of pancreatic 

juice on 167 

Ptyalin 148, 172 

Pulse, the 81 

frequency of S3 

Pupil, movements of 269 

Purkinje's figures 272 

Reflex actions 226 

Respiration. 102 

abnormal 113 

changes in the blood 

in H2 

changes of air in. . . . Ill 
effect of, on the cir- 
culation 118 



INDEX. 



317 



PAGE 

Respiration, effects on, 
produced by mus- 
cular exercise 48 

first, after birth 227 

mechanism of 106 

nervous mechanism 

of 115 

rhythm and number 

of 109 

Retif orm tissue 82 

Retina, the 264 

functions of 270 

Rhythm of respirations. 109 
Rigor mortis 47 

Saliva 147 

Salt 177, 178 

Salts, inorganic 2 

in perspiration 55 

of the red blood-cor- 
puscles 60 

organic crystalline. . 2 
inorganic, of the 

urine 198 

quantity of, in dif- 
ferent foods 136 

Sarcolemma 40 

Schiff s test for uric acid 5 

Sclerotic, the 262 

Scherer's test for leucin 8 
Schwann, white sub- 
stance of 210 

Sebaceous glands 54 

Semicircular canals of 

the ear 276 

Sensations, eccentric ref- 
erence of 224 

Senses, the 259 

Serosity 64 

Serum 63 

Sight 261 

Skin 50 

effect upon, by mus- 
cular exercise 49 



PAGE 

Smell 259 

Sneezing 117, 228 

Soaps 177,178 

Solitary glands 162 

Sounds, articulate 287 

Speech, mechanism of . . 281 

Spermatozoa, the 281 

Spinal accessory, func- 
tion of 252 

Spinal cord 228 

functions of 230 

inhibition of reflex 

actions of 233 

reflex functions of . . 231 
special centres in the 234 

Spleen 201 

functions of 203 

Starch.../. 132 

action of pancreatic 

juice on 168 

Starches, the 174 

Starvation, effects of . . . 137 

Stearin 12, 13, 129 

Stomach, the 158 

digestion of 153 

digestive changes in, 

summary 172 

movements of 159 

Succus entericus 168 

Suprarenals 205 

Sugar 132,177,178 

of milk 10 

9 

dextrin 12 

glycogen ; . 11 

grape 9 

tests for 10 

inosit 10 

Sweat-glands 52 

Sympathetic system 254 

functions of 257 

Syntonin 16 

Taste 260 

buds 145 



318 



INDEX. 



PAGE 

Teeth, the 139 

chemical composi- 
tion and develop- 
ment of 143 

Temperature, changes 
in, produced by mus- 
cular exercise 50 

Terminal organs....... 212 

functions of 224 

Testes, the 303 

Tetanus 45 

Tissue, adipose 29 

connective 25 

lymphoid 28 

muscular 39, 42 

retiform. 28 

yellow elastic 27 

white fibrous 26 

Thermometer scales 308 

Thyroid gland 206 

Tongue, the 144 

Tonsils, the 146 

Tonus, arterial 92 

Touch 261 

Touch-corpuscles 215 

Trachea, the 102 

Trifacial, function of .. . 249 
Trommer's test for grape- 
sugar 10 

Trypsin 168,172 

Tubules, urinary. ... 189 

Tympanum, the 273 

Tyrosin 8 

Hoffman's test for. . 8 
Piria's test for 9 

Ueea 2,64 

amount of 195 

estimation of 196 

sources of 193 

Urasmia 195 

Ureters 192 

Uric acid 64 

Urine 193 



PAGE 

Urine, effect upon, by 

muscular exercise. 49 

secretion of 198 

Umbilical cord, structure 

of 299 

Uterus, the 288 

changes occurring in, 
during impregna- 
tion.., 295 

Vagus, inhibitory action 

of 90 

Vagi, effects of dividing 

the 252 

section of 116 

Valves, in the veins 87 

of the heart 73 

Vas deferens, the 305 

Vaso-motor centres 91 

Vein, portal, what it ab- 
sorbs 177 

Veins, the 69, 86 

valves of the 87 

velocity of blood in.. 88 
Velocity, of the flow of 
blood in the arte- 
ries £0 

of the blood in the 

veins 88 

Vestibule, the, of the ear 275 
Villi of small intestine. . 161 
Vital capacity of the 

chest 110 

Vitelhn 17 

Vitreous humor, the 266 

Vocal cords, the 283 

Voice, different charac- 
ters of 285 

Vomiting 159, 228 

Waem-blooded animals 121 
Water 177, 178 



INDEX. 



319 



PAGE 

Water, quantity of, in 

different foods 136 

White fibrous tissue ... 26 
matter of the spinal 
cord 

White substance of the 
nervous system, 
structure of 216 



229 



PAGE 

Winking 227 

Xanthiit . . 6 

Xanthoprotein reaction 

for proteids 14 

Yellow fibrous tissue.. 27 



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